// This is my answer

#include <cstdlib>
#include <cstring>
#include <string>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <iostream>
#define N 8005

// ---------- decimal lib start ----------

const int PREC = 3001;

class Decimal {
	public:
		Decimal();
		Decimal(const std::string &s);
		Decimal(const char *s);
		Decimal(int x);
		Decimal(long long x);
		Decimal(double x);
		
		bool is_zero() const;
		
		// p (p > 0) is the number of digits after the decimal point
		std::string to_string(int p) const;
		double to_double() const;
		
		friend Decimal operator + (const Decimal &a, const Decimal &b);
		friend Decimal operator + (const Decimal &a, int x);
		friend Decimal operator + (int x, const Decimal &a);
		friend Decimal operator + (const Decimal &a, long long x);
		friend Decimal operator + (long long x, const Decimal &a);
		friend Decimal operator + (const Decimal &a, double x);
		friend Decimal operator + (double x, const Decimal &a);
		
		friend Decimal operator - (const Decimal &a, const Decimal &b);
		friend Decimal operator - (const Decimal &a, int x);
		friend Decimal operator - (int x, const Decimal &a);
		friend Decimal operator - (const Decimal &a, long long x);
		friend Decimal operator - (long long x, const Decimal &a);
		friend Decimal operator - (const Decimal &a, double x);
		friend Decimal operator - (double x, const Decimal &a);
		
		friend Decimal operator * (const Decimal &a, int x);
		friend Decimal operator * (int x, const Decimal &a);
		
		friend Decimal operator / (const Decimal &a, int x);
		
		friend bool operator < (const Decimal &a, const Decimal &b);
		friend bool operator > (const Decimal &a, const Decimal &b);
		friend bool operator <= (const Decimal &a, const Decimal &b);
		friend bool operator >= (const Decimal &a, const Decimal &b);
		friend bool operator == (const Decimal &a, const Decimal &b);
		friend bool operator != (const Decimal &a, const Decimal &b);
		
		Decimal & operator += (int x);
		Decimal & operator += (long long x);
		Decimal & operator += (double x);
		Decimal & operator += (const Decimal &b);
		
		Decimal & operator -= (int x);
		Decimal & operator -= (long long x);
		Decimal & operator -= (double x);
		Decimal & operator -= (const Decimal &b);
		
		Decimal & operator *= (int x);
		
		Decimal & operator /= (int x);
		
		friend Decimal operator - (const Decimal &a);
		
		// These can't be called
		friend Decimal operator * (const Decimal &a, double x);
		friend Decimal operator * (double x, const Decimal &a);
		friend Decimal operator / (const Decimal &a, double x);
		Decimal & operator *= (double x);
		Decimal & operator /= (double x);
		
	private:
		static const int len = PREC / 9 + 1;
		static const int mo = 1000000000;
		
		static void append_to_string(std::string &s, long long x);
		
		bool is_neg;
		long long integer;
		int data[len];
		
		void init_zero();
		void init(const char *s);
};

Decimal::Decimal() {
	this->init_zero();
}

Decimal::Decimal(const char *s) {
	this->init(s);
}

Decimal::Decimal(const std::string &s) {
	this->init(s.c_str());
}

Decimal::Decimal(int x) {
	this->init_zero();
	
	if (x < 0) {
		is_neg = true;
		x = -x;
	}
	
	integer = x;
}

Decimal::Decimal(long long x) {
	this->init_zero();
	
	if (x < 0) {
		is_neg = true;
		x = -x;
	}
	
	integer = x;
}

Decimal::Decimal(double x) {
	this->init_zero();
	
	if (x < 0) {
		is_neg = true;
		x = -x;
	}
	
	integer = (long long)x;
	x -= integer;
	
	for (int i = 0; i < len; i++) {
		x *= mo;
		if (x < 0) x = 0;
		data[i] = (int)x;
		x -= data[i];
	}
}

void Decimal::init_zero() {
	is_neg = false;
	integer = 0;
	memset(data, 0, len * sizeof(int));
}

bool Decimal::is_zero() const {
	if (integer) return false;
	for (int i = 0; i < len; i++) {
		if (data[i]) return false;
	}
	return true;
}

void Decimal::init(const char *s) {
	this->init_zero();
	
	is_neg = false;
	integer = 0;
	
	// find the first digit or the negative sign
	while (*s != 0) {
		if (*s == '-') {
			is_neg = true;
			++s;
			break;
		} else if (*s >= 48 && *s <= 57) {
			break;
		}
		++s;
	}
	
	// read the integer part
	while (*s >= 48 && *s <= 57) {
		integer = integer * 10 + *s - 48;
		++s;
	}
	
	// read the decimal part
	if (*s == '.') {
		int pos = 0;
		int x = mo / 10;
		
		++s;
		while (pos < len && *s >= 48 && *s <= 57) {
			data[pos] += (*s - 48) * x;
			++s;
			x /= 10;
			if (x == 0) {
				++pos;
				x = mo / 10;
			}
		}
	}
}

void Decimal::append_to_string(std::string &s, long long x) {
	if (x == 0) {
		s.append(1, 48);
		return;
	}
	
	char _[30];
	int cnt = 0;
	while (x) {
		_[cnt++] = x % 10;
		x /= 10;
	}
	while (cnt--) {
		s.append(1, _[cnt] + 48);
	}
}

std::string Decimal::to_string(int p) const {
	std::string ret;
	
	if (is_neg && !this->is_zero()) {
		ret = "-";
	}
	
	append_to_string(ret, this->integer);
	
	ret.append(1, '.');
	
	for (int i = 0; i < len; i++) {
		// append data[i] as "%09d"
		int x = mo / 10;
		int tmp = data[i];
		while (x) {
			ret.append(1, 48 + tmp / x);
			tmp %= x;
			x /= 10;
			if (--p == 0) {
				break;
			}
		}
		if (p == 0) break;
	}
	
	if (p > 0) {
		ret.append(p, '0');
	}
	
	return ret;
}

double Decimal::to_double() const {
	double ret = integer;
	
	double k = 1.0;
	for (int i = 0; i < len; i++) {
		k /= mo;
		ret += k * data[i];
	}
	
	if (is_neg) {
		ret = -ret;
	}
	
	return ret;
}

bool operator < (const Decimal &a, const Decimal &b) {
	if (a.is_neg != b.is_neg) {
		return a.is_neg && (!a.is_zero() || !b.is_zero());
	} else if (!a.is_neg) {
		// a, b >= 0
		if (a.integer != b.integer) {
			return a.integer < b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] < b.data[i];
			}
		}
		return false;
	} else {
		// a, b <= 0
		if (a.integer != b.integer) {
			return a.integer > b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] > b.data[i];
			}
		}
		return false;
	}
}

bool operator > (const Decimal &a, const Decimal &b) {
	if (a.is_neg != b.is_neg) {
		return !a.is_neg && (!a.is_zero() || !b.is_zero());
	} else if (!a.is_neg) {
		// a, b >= 0
		if (a.integer != b.integer) {
			return a.integer > b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] > b.data[i];
			}
		}
		return false;
	} else {
		// a, b <= 0
		if (a.integer != b.integer) {
			return a.integer < b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] < b.data[i];
			}
		}
		return false;
	}
}

bool operator <= (const Decimal &a, const Decimal &b) {
	if (a.is_neg != b.is_neg) {
		return a.is_neg || (a.is_zero() && b.is_zero());
	} else if (!a.is_neg) {
		// a, b >= 0
		if (a.integer != b.integer) {
			return a.integer < b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] < b.data[i];
			}
		}
		return true;
	} else {
		// a, b <= 0
		if (a.integer != b.integer) {
			return a.integer > b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] > b.data[i];
			}
		}
		return true;
	}
}

bool operator >= (const Decimal &a, const Decimal &b) {
	if (a.is_neg != b.is_neg) {
		return !a.is_neg || (a.is_zero() && b.is_zero());
	} else if (!a.is_neg) {
		// a, b >= 0
		if (a.integer != b.integer) {
			return a.integer > b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] > b.data[i];
			}
		}
		return true;
	} else {
		// a, b <= 0
		if (a.integer != b.integer) {
			return a.integer < b.integer;
		}
		for (int i = 0; i < Decimal::len; i++) {
			if (a.data[i] != b.data[i]) {
				return a.data[i] < b.data[i];
			}
		}
		return true;
	}
}

bool operator == (const Decimal &a, const Decimal &b) {
	if (a.is_zero() && b.is_zero()) return true;
	if (a.is_neg != b.is_neg) return false;
	if (a.integer != b.integer) return false;
	for (int i = 0; i < Decimal::len; i++) {
		if (a.data[i] != b.data[i]) return false;
	}
	return true;
}

bool operator != (const Decimal &a, const Decimal &b) {
	return !(a == b);
}

Decimal & Decimal::operator += (long long x) {
	if (!is_neg) {
		if (integer + x >= 0) {
			integer += x;
		} else {
			bool last = false;
			for (int i = len - 1; i >= 0; i--) {
				if (last || data[i]) {
					data[i] = mo - data[i] - last;
					last = true;
				} else {
					last = false;
				}
			}
			integer = -x - integer - last;
			is_neg = true;
		}
	} else {
		if (integer - x >= 0) {
			integer -= x;
		} else {
			bool last = false;
			for (int i = len - 1; i >= 0; i--) {
				if (last || data[i]) {
					data[i] = mo - data[i] - last;
					last = true;
				} else {
					last = false;
				}
			}
			integer = x - integer - last;
			is_neg = false;
		}
	}
	return *this;
}

Decimal & Decimal::operator += (int x) {
	return *this += (long long)x;
}

Decimal & Decimal::operator -= (int x) {
	return *this += (long long)-x;
}

Decimal & Decimal::operator -= (long long x) {
	return *this += -x;
}

Decimal & Decimal::operator /= (int x) {
	if (x < 0) {
		is_neg ^= 1;
		x = -x;
	}
	
	int last = integer % x;
	integer /= x;
	
	for (int i = 0; i < len; i++) {
		long long tmp = 1LL * last * mo + data[i];
		data[i] = tmp / x;
		last = tmp - 1LL * data[i] * x;
	}
	
	if (is_neg && integer == 0) {
		int i;
		for (i = 0; i < len; i++) {
			if (data[i] != 0) {
				break;
			}
		}
		if (i == len) {
			is_neg = false;
		}
	}
	
	return *this;
}

Decimal & Decimal::operator *= (int x) {
	if (x < 0) {
		is_neg ^= 1;
		x = -x;
	} else if (x == 0) {
		init_zero();
		return *this;
	}
	
	int last = 0;
	for (int i = len - 1; i >= 0; i--) {
		long long tmp = 1LL * data[i] * x + last;
		last = tmp / mo;
		data[i] = tmp - 1LL * last * mo;
	}
	integer = integer * x + last;
	
	return *this;
}

Decimal operator - (const Decimal &a) {
	Decimal ret = a;
	// -0 = 0
	if (!ret.is_neg && ret.integer == 0) {
		int i;
		for (i = 0; i < Decimal::len; i++) {
			if (ret.data[i] != 0) break;
		}
		if (i < Decimal::len) {
			ret.is_neg = true;
		}
	} else {
		ret.is_neg ^= 1;
	}
	return ret;
}

Decimal operator + (const Decimal &a, int x) {
	Decimal ret = a;
	return ret += x;
}

Decimal operator + (int x, const Decimal &a) {
	Decimal ret = a;
	return ret += x;
}

Decimal operator + (const Decimal &a, long long x) {
	Decimal ret = a;
	return ret += x;
}

Decimal operator + (long long x, const Decimal &a) {
	Decimal ret = a;
	return ret += x;
}

Decimal operator - (const Decimal &a, int x) {
	Decimal ret = a;
	return ret -= x;
}

Decimal operator - (int x, const Decimal &a) {
	return -(a - x);
}

Decimal operator - (const Decimal &a, long long x) {
	Decimal ret = a;
	return ret -= x;
}

Decimal operator - (long long x, const Decimal &a) {
	return -(a - x);
}

Decimal operator * (const Decimal &a, int x) {
	Decimal ret = a;
	return ret *= x;
}

Decimal operator * (int x, const Decimal &a) {
	Decimal ret = a;
	return ret *= x;
}

Decimal operator / (const Decimal &a, int x) {
	Decimal ret = a;
	return ret /= x;
}

Decimal operator + (const Decimal &a, const Decimal &b) {
	if (a.is_neg == b.is_neg) {
		Decimal ret = a;
		bool last = false;
		for (int i = Decimal::len - 1; i >= 0; i--) {
			ret.data[i] += b.data[i] + last;
			if (ret.data[i] >= Decimal::mo) {
				ret.data[i] -= Decimal::mo;
				last = true;
			} else {
				last = false;
			}
		}
		ret.integer += b.integer + last;
		return ret;
	} else if (!a.is_neg) {
		// a - |b|
		return a - -b;
	} else {
		// b - |a|
		return b - -a;
	}
}

Decimal operator - (const Decimal &a, const Decimal &b) {
	if (!a.is_neg && !b.is_neg) {
		if (a >= b) {
			Decimal ret = a;
			bool last = false;
			for (int i = Decimal::len - 1; i >= 0; i--) {
				ret.data[i] -= b.data[i] + last;
				if (ret.data[i] < 0) {
					ret.data[i] += Decimal::mo;
					last = true;
				} else {
					last = false;
				}
			}
			ret.integer -= b.integer + last;
			return ret;
		} else {
			Decimal ret = b;
			bool last = false;
			for (int i = Decimal::len - 1; i >= 0; i--) {
				ret.data[i] -= a.data[i] + last;
				if (ret.data[i] < 0) {
					ret.data[i] += Decimal::mo;
					last = true;
				} else {
					last = false;
				}
			}
			ret.integer -= a.integer + last;
			ret.is_neg = true;
			return ret;
		}
	} else if (a.is_neg && b.is_neg) {
		// a - b = (-b) - (-a)
		return -b - -a;
	} else if (a.is_neg) {
		// -|a| - b
		return -(-a + b);
	} else {
		// a - -|b|
		return a + -b;
	}
}

Decimal operator + (const Decimal &a, double x) {
	return a + Decimal(x);
}

Decimal operator + (double x, const Decimal &a) {
	return Decimal(x) + a;
}

Decimal operator - (const Decimal &a, double x) {
	return a - Decimal(x);
}

Decimal operator - (double x, const Decimal &a) {
	return Decimal(x) - a;
}

Decimal & Decimal::operator += (double x) {
	*this = *this + Decimal(x);
	return *this;
}

Decimal & Decimal::operator -= (double x) {
	*this = *this - Decimal(x);
	return *this;
}

Decimal & Decimal::operator += (const Decimal &b) {
	*this = *this + b;
	return *this;
}

Decimal & Decimal::operator -= (const Decimal &b) {
	*this = *this - b;
	return *this;
}

// ---------- decimal lib end ----------
#define double long double
using namespace std;
Decimal ans;
struct node{
	double x,y;
}q[N];
int n,m,k,p,pos,lmt;
int tot=1,h[N],s[N],a[N][25];
double maxx,f[N][25];
int Q[N],hed,til;
double slope(node aa,node bb){
	return (aa.y-bb.y)/(aa.x-bb.x);
}
Decimal calc(int i,int j){
	if(!j)return h[1];
	return (calc(a[i][j],j-1)+s[i]-s[a[i][j]])/(i-a[i][j]+1);
}
signed main(){
	cin>>n>>k>>p>>h[1];
	for(int i=2;i<=n;++i){
		cin>>h[i];
		if(h[i]>h[1])h[++tot]=h[i];
	} n=tot; sort(h+1,h+1+n);
	for(int i=1;i<=n;++i)s[i]=s[i-1]+h[i];
	k=min(k,n);
	for(int i=1;i<=n;++i)f[i][0]=h[1];
	lmt=min(k,14);
	for(int j=1;j<=lmt;++j){
		Q[1]=1; hed=1; til=1;
		for(int i=1;i<=n;++i){
			q[i]=(node){i-1,s[i]-f[i][j-1]};
		}
		for(int i=2;i<=n;++i){
			node cur=(node){i,s[i]};
			while(hed<til && slope(cur,q[Q[hed]])<slope(cur,q[Q[hed+1]]))++hed;
			a[i][j]=Q[hed];
			f[i][j]=(s[i]-s[Q[hed]]+f[Q[hed]][j-1])/(i-Q[hed]+1);
			while(hed<til && slope(q[Q[til]],q[Q[til-1]])>slope(q[Q[til]],q[i]))--til;
			Q[++til]=i;
		}
	} m=n-k+lmt;
	for(int j=0;j<=lmt;++j){
		if(f[m][j]>maxx){
			maxx=f[m][j];
			pos=j;
		}
	}
	ans=calc(m,pos);
	for(int i=m+1;i<=n;++i)ans=(ans+h[i])/2;
	cout<<ans.to_string(p<<1);
	return 0;
}