#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(x) (x).begin(), (x).end()
const int N = 1e3 + 7;
int n, k;
ll t, a[N];
ll cdiv(ll x, ll y) {
if (y == 0) return 0;
return (x + y - 1) / y;
}
int main() {
cin.tie(0)->sync_with_stdio(false);
cin >> n >> k >> t;
for (int i = 1; i <= n; i++)
cin >> a[i];
a[0] = -1e18, a[n + 1] = 1e18;
ll ans = 0;
int l = k, r = k;
for (int i = 1; i < n; i++) {
ll x = cdiv(a[r] - a[l - 1], 2 * t * i);
ll y = cdiv(a[r + 1] - a[l], 2 * t * i);
if (x < y) {
l--;
ans = max(ans, x);
} else {
r++;
ans = max(ans, y);
}
}
cout << ans << '\n';
return 0;
}
