#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 100005;
const ll inf = 1e18;
ll pos[MAXN], T;
int N, K;
ll cdiv(ll a, ll b){
return (a + b - 1) / b;
}
bool test(ll v){
int l = K, r = K;
while (l != 1 || r != N){
ll ld = pos[r] - pos[l - 1], rd = pos[r + 1] - pos[l], spt = T * (r - l + 1);
if (ld < rd){
if (cdiv(ld, 2 * v) > spt) return 0;
l--;
}
else{
if (cdiv(rd, 2 * v) > spt) return 0;
r++;
}
}
return 1;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> N >> K >> T;
for (int i = 1; i <= N; i++) cin >> pos[i];
pos[0] = -inf; pos[N + 1] = inf;
ll lo = 1, hi = 1e9, ans;
while (lo <= hi){
ll m = (lo + hi) >> 1;
if (test(m)){
ans = m; hi = m - 1;
}
else lo = m + 1;
}
cout << ans;
}
