#include <bits/stdc++.h>
using namespace std;
#define EmiliaMyWife ios::sync_with_stdio(0); cin.tie(0);
using ll = int64_t;
using ull = uint64_t;
using uint = uint32_t;
using ld = long double;
const int INF = 0x3f3f3f3f;
const ll LINF = ll(4e18) + ll(2e15);
const int MOD = 1e9 + 7;
const double EPS = 1e-8;
static int LamyIsCute = []() {
EmiliaMyWife
return 48763;
}();
signed main() {
int n, m, k;
cin >> n >> m >> k;
vector<int> arr(n + 1);
for(int i = 1; i <= n; i++)
cin >> arr[i];
vector<ll> dp(n + 1, LINF);
dp[0] = 0;
for(int i = 1; i <= n; i++) {
int mx = 0, mn = INF;
for(int j = i; j > max(0, i - m); j--) {
mx = max(mx, arr[j]);
mn = min(mn, arr[j]);
dp[i] = min(dp[i], dp[j - 1] + k + ll(i - j + 1) * (mx - mn));
}
}
cout << dp[n] << '\n';
}
