#include <bits/stdc++.h>
using namespace std;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second
#define FILL(a, b) memset(a, b, sizeof(a))

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

const int INF = 1e9 + 7;

bool bad(int a, int b, int c, int d)
{
	return a == c || a == d || b == c || b == d;
}


int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	LL n, k, avg;
	cin >> n >> k >> avg;
	VI x(n);
	set<pair<int, PII>> b;
	LL sum = 0;
	FOR (i, 0, n)
	{
		cin >> x[i];
		sum += x[i];
		FOR (j, 0, i)
		{
			b.insert({x[i] + x[j], {i, j}});
		}
	}
	double ans = double(abs(sum - avg * n)) / n;
	if (k >= 1)
	{
		LL target = avg * (n - 1);
		FOR (i, 0, n)
		{
			sum -= x[i];
			ans = min(ans, double(abs(sum - target)) / (n - 1));
			sum += x[i];
		}
	}
	if (k >= 2)
	{
		LL target = avg * (n - 2);
		for (auto [val, p] : b)
		{
			sum -= val;
			ans = min(ans, double(abs(sum - target)) / (n - 2));
			sum += val;
		}
	}
	if (k >= 3)
	{
		LL target = avg * (n - 3);
		FOR (i, 0, n)
		{
			sum -= x[i];
			FOR (j, 0, i) b.erase({x[i] + x[j], {i, j}});
			FOR (j, i + 1, n) b.erase({x[i] + x[j], {j, i}});
			
			auto it = b.lower_bound({sum - target, {-1, -1}});
			if (it != b.end())
			{
				sum -= it->first;
				ans = min(ans, double(abs(sum - target)) / (n - 3));
				sum += it->first;
			}
			if (it != b.begin())
			{
				it--;
				sum -= it->first;
				ans = min(ans, double(abs(sum - target)) / (n - 3));
				sum += it->first;
			}
			FOR (j, 0, i) b.insert({x[i] + x[j], {i, j}});
			FOR (j, i + 1, n) b.insert({x[i] + x[j], {j, i}});
			
			sum += x[i];
		}		
	}
	if (k >= 4)
	{
		LL target = avg * (n - 4);
		for (auto [val, p] : b)
		{
			int v1 = p.F, v2 = p.S;
			sum -= val;
			
			auto it = b.lower_bound({sum - target, {-1, -1}});
			auto it2 = it;
			while (it2 != b.end() && bad(v1, v2, it2->S.F, it2->S.S)) it2++;
			if (it2 != b.end())
			{
				sum -= it2->first;
				ans = min(ans, double(abs(sum - target)) / (n - 4));
				sum += it2->first;
			}
			it2 = it;
			if (it2 != b.begin())
			{
				it2--;
				while (it2 != b.begin() && bad(v1, v2, it2->S.F, it2->S.S)) it2--;	
				if (!bad(v1, v2, it2->S.F, it2->S.S))
				{
					sum -= it2->first;
					ans = min(ans, double(abs(sum - target)) / (n - 4));
					sum += it2->first;
				}
			}
			sum += val;
		}		
	}
	cout << fixed << setprecision(10) << ans << '\n';
	
	
	
	return 0;
}