#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main () {
    ll N, K;
    cin >> N >> K;
    std::vector<ll> A(N);
    for (auto& a : A) {
        cin >> a;
    }
    ll ok = 0, ng = (ll)1e16;
    while (abs(ok - ng) > 1) {
        ll mu = (ng + ok) / 2;
        ll pll = 0;
        ll k = K;
        for (ll i = 0; i < N; i ++) {
            ll ad = max(0ll, mu - (A[i] + pll));
            ll c = (ad + i) / (i + 1);
            k -= c;
            pll += c * (i + 1);
        }
        if (k >= 0) {
            ok = mu;
        } else {
            ng = mu;
        }
    }
    cout << ok << endl;
}