#include <bits/stdc++.h>
#define pb push_back
#define all(v) ((v).begin(), (v).end())
#define sortv(v) sort(all(v))
#define sz(v) ((int)(v).size())
#define uniqv(v) (v).erase(unique(all(v)), (v).end())
#define umax(a, b) (a)=max((a), (b))
#define umin(a, b) (a)=min((a), (b))
#define FOR(i,a,b) for(int i = (a); i <= (b); i++)
#define rep(i,n) FOR(i,1,n)
#define rep0(i,n) FOR(i,0,(int)(n)-1)
#define FI first
#define SE second
#define INF 2000000000
#define INFLL 1000000000000000000LL
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int MAX_N = 20000;
int N, M;
ll K;
ll DP[MAX_N+1];
ll arr[MAX_N+1];
int main(){
cin>>N>>M>>K;
for(int i=1; i<=N; i++){
cin>>arr[i];
DP[i] = DP[i-1] + K;
ll mn=arr[i], mx=arr[i];
for(int j=i-1; j>=max(1, i - M + 1); j--){
mn = min(arr[j], mn); mx = max(arr[j], mx);
DP[i] = min(DP[i], K + DP[j-1] + (ll)(mx - mn) * (ll)(i - j + 1));
}
}
cout<<DP[N];
return 0;
}
