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

int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  ll n,k;
  cin>>n>>k;
  vector<ll> A(n);
  rep(i,n) cin>>A[i];
  
  auto f=[&](ll x)->bool{
    ll tmp=k;
    ll sum=0;
    rep(i,n){
      if(A[i]+sum>=x) continue;
      ll t=((x-A[i]-sum+i)/(i+1));
      tmp-=t;
      sum+=t*(i+1);
    }
    if(tmp>=0) return true;
    return false;
  };
  
  ll ok=0,ng=1e18;
  while(ng-ok>1){
    ll mid=(ok+ng)/2;
    if(f(mid)) ok=mid;
    else ng=mid;
  }
  cout<<ok<<endl;

  return 0;
}