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

using ll = long long;

bool chmax(auto &a, auto b) { return a < b ? a = b, 1 : 0; }
bool chmin(auto &a, auto b) { return a > b ? a = b, 1 : 0; }

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll N, K, X; cin >> N >> K >> X;
    vector<ll> A(N);
    for (auto &&a : A) cin >> a;

    ll ans = -1LL << 60;
    multiset<ll> high;
    ll sum = 0;
    for (int i = 0; i < K; ++i) {
        high.insert(A[i]);
        sum += A[i];
        chmax(ans, sum - X * (i + 1));
    }
    for (int i = K; i < N; ++i) {
        if (A[i] > *high.begin()) {
            sum -= *high.begin();
            high.erase(high.begin());
            sum += A[i];
            high.insert(A[i]);
        }
        chmax(ans, sum - X * (i + 1));
    }
    cout << ans << '\n';
}