#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<int(n);i++)

int main(){
  int n,k;
  cin>>n>>k;
  vector<ll> a(n);
  rep(i,n) cin>>a.at(i);
  ll up=1e15;
  ll dw=0;
  while(up-dw>1){
    ll md=(up+dw)/2;
    ll ad=0;
    ll ct=0;
    rep(i,n){
      if(a.at(i)+ad<md){
        ct+=(md-(a.at(i)+ad)+i)/(i+1);
        ad+=((md-(a.at(i)+ad)+i)/(i+1))*(i+1);
      }
      if(ct>k) break;
    }
    if(ct>k) up=md;
    else dw=md;
  }
  cout<<dw<<'\n';
}