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

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    ll ans = -1LL << 60;
    multiset<ll> st;
    ll n, k, x;
    cin >> n >> k >> x;
    ll s = 0;
    rep(i, n) {
        ll a;
        cin >> a;
        s += a;
        st.insert(a);
        if (st.size() > k) {
            s -= *st.begin();
            st.erase(st.begin());
        }
        ans = max(ans, s - x * (i + 1));
    }
    cout << ans << endl;
    return 0;
}