#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF (int)1e18
#define f first
#define s second
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
int n, m, k;
const int N = 2e4 + 69;
int dp[N], a[N];
void Solve()
{
cin >> n >> m >> k;
for (int i = 1; i <= n; i++){
cin >> a[i];
}
for (int i = 1; i <= n; i++){
dp[i] = INF;
int mi = INF, mx = 0;
for (int j = i; j >= 1; j--){
if (i - j + 1 > m) break;
mi = min(mi, a[j]);
mx = max(mx, a[j]);
int cost = k + ((i - j + 1) * (mx - mi));
// cout << mx << " " << mi << " :cost << " ";
dp[i] = min(dp[i], dp[j - 1] + cost);
}
// cout << dp[i] << "\n";
}
cout << dp[n] << "\n";
}
int32_t main()
{
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
for(int i = 1; i <= t; i++)
{
//cout << "Case #" << i << ": ";
Solve();
}
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
return 0;
}
