#include <iostream>
#include <algorithm>
constexpr int N(1e5+10);
using ll=long long;
int l,m;ll b[N],c[N];
bool check()
{
	static int s1[N],s2[N];int t1(0),t2(0);static ll mx[N];mx[m]=c[m];for(int i(m-1);i>=0;--i) mx[i]=std::max(mx[i+1],c[i]);
	s1[t1=1]=0;for(int i(1);i<=l;++i){while(t1 && b[s1[t1]]>b[i]) --t1;s1[++t1]=i;}
	s2[t2=1]=l;for(int i(l-1);i>=0;--i){while(t2 && b[s2[t2]]>=b[i]) --t2;s2[++t2]=i;}
	if(b[s1[1]]+mx[0]>0) return false;if(b[l]+c[m]>0) return false;
	int t(0);
	for(int i(t2);i>1;--i)
	{
		ll v(*std::max_element(b+s2[i],b+s2[i-1]+1));
		while(c[t]+v>0)
		{
			if(t==m) return false;
			++t;if(c[t]+b[s2[i]]>0) return false;
		}
	}
	for(int i(2);i<=t1;++i)
	{
		int k(s1[i]);
		int t0(t);while(mx[t0]+b[k]>0) ++t0;
		ll v(*std::max_element(b+s1[i-1],b+s1[i]+1));
		while(t0<=m && c[t0]+v>0) ++t0;if(t0>m) return false;
		t=t0;
	}
	return true;
}
int main()
{
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int n,k;ll T;std::cin>>n>>k>>T;T*=2;
	static ll a[N];
	for(int i(1);i<=n;++i) std::cin>>a[i];
	ll el(0),er(1e9),mid,ans(0);
	while(el<=er)
	{
		mid=(el+er)>>1;l=0;m=0;
		for(int i(k-1);i;--i) b[++l]=a[k]-a[i]-(k-i)*T*mid;
		for(int i(k+1);i<=n;++i) c[++m]=a[i]-a[k]-(i-k)*T*mid;
		if(check()){er=mid-1,ans=mid;}
		else el=mid+1;
	}
	std::cout<<ans<<std::endl;
	return 0;
}