#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 dp[N][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];
memset(dp, 0x3f, sizeof(dp));
dp[0][n] = 0;
for (int l = 1; l <= n; l++) {
for (int r = n; r >= 1; r--) {
dp[l][r] = max(cdiv(a[r] - a[l], 2 * t * (r - l)), min(dp[l - 1][r], dp[l][r + 1]));
}
}
cout << dp[k][k] << '\n';
return 0;
}
