#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e3 + 5;
ll n, k, t;
ll x[N];
bool dp[N][N];
bool check(__int128 v) {
memset(dp, 0, sizeof(dp));
dp[k][k] = 1;
for (int h = 1; h <= n; ++h) {
for (int l = 1; l + h - 1 <= n; ++l) {
int r = l + h - 1;
if (dp[l][r] == 0) continue;
if (r < n && x[r + 1] - x[l] <= 2 * v * (r - l + 1) * t) dp[l][r + 1] = 1;
if (l > 1 && x[r] - x[l - 1] <= 2 * v * (r - l + 1) * t) dp[l - 1][r] = 1;
}
}
return dp[1][n];
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> k >> t;
for (int i = 1; i <= n; ++i) cin >> x[i];
ll l = 0, r = 1e9, sol = -1;
while (l <= r) {
ll m = (l + r) / 2;
if (check(m)) {
sol = m;
r = m - 1;
} else {
l = m + 1;
}
}
cout << sol << "\n";
return 0;
}
