#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000000;
int main(){
  int N, K;
  cin >> N >> K;
  vector<long long> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  long long tv = 0, fv = INF;
  while (fv - tv > 1){
    long long mid = (tv + fv) / 2;
    long long add = 0, cnt = 0;
    for (int i = 0; i < N; i++){
      if (A[i] < mid - add){
        long long c = (mid - add - A[i] + i) / (i + 1);
        add += c * (i + 1);
        cnt += c;
      }
    }
    if (cnt <= K){
      tv = mid;
    } else {
      fv = mid;
    }
  }
  cout << tv << endl;
}