#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for (ll i = a; i < b; i++)
using ll = long long;

int main(){
    int n, k, x;
    cin >> n >> k >> x;
    vector<ll> a(n);
    rep(i, 0, n)  cin >> a[i];
    ll ans = -1e9, s = 0;
    multiset<int> st;
    rep(i, 0, n) {
        ll j = i + 1;
        int now = a[i];
        ll mi = min(ll(k), j);
        int sz = st.size();
        if(sz >= mi) {
            int r = *st.begin();
            if(r < now) {
                st.insert(now);
                s += now;
                s -= r;
                st.erase(st.begin());
            }
        }
        else {
            st.insert(now);
            s += now;
        }
        ans = max(ans, s - x * j);
    }
    cout << ans << endl;
}