#include<bits/stdc++.h>
using namespace std;
constexpr int Inf = 1000000010;
constexpr long long INF= 2000000000000000000;

template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }

template<typename T,typename U>
T modpow(T N, U P, T M = -1) {
    if(P < 0) return 0;
    T ret = 1;
    if(M != -1) ret %= M;
    while(P) {
        if(P & 1) {
            if(M == -1) ret *= N;
            else ret = ret * N % M;
        }
        P /= 2;
        if(M == -1) N *= N;
        else N = N * N % M;
    }
    return ret;
}

constexpr long long MOD = 998244353;

int main() {
    int n;
    long long k;
    cin >> n >> k;
    vector<long long> vec(n);
    for(auto& x: vec) cin >> x;

    long long ok = 0;
    long long ng = INF;
    while(ng - ok > 1) {
        long long mid = (ok + ng) / 2;
        long long sum = 0;
        long long count = 0;
        for(long long i = 0;i < n;i++) {
            if(vec[i] + sum < mid) {
                count += (mid - (vec[i] + sum) + i) / (i + 1);
                sum += (mid - (vec[i] + sum) + i) / (i + 1) * (i + 1); 
            }
            if(count > k) break;
        }

        if(count > k) ng = mid;
        else ok = mid;
    }

    cout << ok << endl;
}