#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<(n);i++)

int main(){
    int n, k;
    ll x;
    cin >> n >> k >> x;
    vector<ll> a(n);
    rep(i,n) cin >> a[i];

    ll ans = -2e18, sum = 0;
    priority_queue<ll, vector<ll>, greater<ll>> q;
    rep(i,n){
        q.push(a[i]);
        sum += a[i];
        if(k<q.size()){
            sum -= q.top();
            q.pop();
        }
        if(ans<sum-x*(i+1)) ans = sum-x*(i+1);
    }

    cout << ans << endl;

}