#ifndef hari64
#include <bits/stdc++.h>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
#define debug(...)
#else
#include "util/viewer.hpp"
#define debug(...) viewer::_debug(__LINE__, #__VA_ARGS__, __VA_ARGS__)
#endif
using namespace std;
constexpr int INF = 1001001001;
constexpr long long INFll = 1001001001001001001;
template <class T>
bool chmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    return a > b ? a = b, 1 : 0;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    long long N, K;
    cin >> N >> K;
    vector<long long> As(N);
    for (int i = 0; i < N; i++) {
        cin >> As[i];
    }

    auto is_ok = [&](long long x) -> bool {
        long long add = 0;
        long long cnt = 0;
        for (long long i = 0; i < N; i++) {
            if (As[i] + add < x) {
                cnt += (x - As[i] - add + i) / (i + 1);
                add += (i + 1) * ((x - As[i] - add + i) / (i + 1));
            }
        }
        debug(x, add, cnt);
        return cnt <= K;
    };

    long long ok, ng;
    ok = 0;
    ng = INFll;
    while (abs(ok - ng) > 1) {
        long long mid = (ok + ng) / 2;
        if (is_ok(mid)) {
            ok = mid;
        } else {
            ng = mid;
        }
    }

    cout << ok << endl;

    return 0;
}