#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int MAXN = 1e5 + 5;

struct Data
{
	ll a,b;
	bool type(void) const { return a <= b;}
};
bool operator < (Data A,Data B)
{
	if(A.type() != B.type()) return A.type();
	return A.type()? A.a < B.a: A.b > B.b;
}
Data operator + (Data A,Data B)
{
	ll sum = - A.a + A.b - B.a + B.b;
	ll mn = min(- A.a, - A.a + A.b - B.a);
	return Data{-mn, sum - mn};
}

void trim(vector<Data> &A)
{
	reverse(A.begin(), A.end());
	int pos = -1;
	for(int i=0; i<(int)A.size(); ++i)
	{
		while(pos >= 0 && A[pos] < A[i])
			A[i] = A[i] + A[pos--];
		A[++pos] = A[i];
	}
	A.resize(pos+1);
	reverse(A.begin(), A.end());
}

int n,m,d;
int a[MAXN];

bool chk(ll lim)
{
	lim = lim * 2 * m;
	
	vector<Data> A, B;
	for(int i=d; i>1; --i)
		A.push_back({a[i] - a[i-1], lim});
	for(int i=d; i<n; ++i)
		B.push_back({a[i+1] - a[i], lim});
	trim(A); trim(B);
	
	vector<Data> res(A.size() + B.size());
	merge(A.begin(), A.end(), B.begin(), B.end(), res.begin());
	trim(res);
	
	Data sum{0, lim};
	for(auto t: res)
		sum = sum + t;
	return sum.a == 0;
}

int main(void)
{
	scanf("%d%d%d",&n,&d,&m);
	for(int i=1; i<=n; ++i)
		scanf("%d",&a[i]);
	
	int l = 0, r = 1e9;
	while(l<r)
	{
		int mid = (l+r)>>1;
		if(chk(mid)) r = mid;
		else l = mid+1;
	}
	printf("%d\n",l);
	return 0;
}