#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
const ll N = 1e5 + 5;
ll n, k, t, a[N], b[N];
bool check(ll s) {
if (s * t > 1e9) return 1;
for (ll i = 0; i < n; i++) b[i] = a[i] - 2 * s * t * i;
ll l = k, r = k;
while (l != 0 || r != n - 1) {
if (l > 0 && b[l - 1] >= b[r]) l--;
else if (r < n - 1 && b[r + 1] <= b[l]) r++;
else return 0;
}
return 1;
}
signed main() {
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cin >> n >> k >> t, k--;
for (ll i = 0; i < n; i++) cin >> a[i];
ll l = -1, r = 1e9 / t + 5;
check(3);
while (l + 1 < r) {
ll m = (l + r) / 2;
(check(m) ? r : l) = m;
}
cout << r;
}
