#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
using ll=long long;
using ld=double;
ld pie=3.14159265359;
ll mod=998244353;
ll inf=10000000000000000;
int main(){
    ll n,k;
    cin >> n >> k;
    vector<ll>a(n);
    for (ll i = 0; i < n; i++)
    {
        cin >> a[i];
    }
    ll left=0,right=inf;
    while (right-left>1)
    {
        ll mid=(right+left)/2;
        vector<ll>b=a;
        ll now=0;
        ll nec=0;
        for (ll i = 0; i < n; i++)
        {
            if (a[i]+now<mid)
            {
                ll y=0;
                y+=(mid-now-a[i])/(i+1);
                if ((mid-now-a[i])%(i+1)!=0)
                {
                    y+=1;
                }
                nec+=y;
                now+=y*(i+1);
            }
            if (nec>k)
            {
                break;
            }
        }
        if (nec>k)
        {
            right=mid;
        }else{
            left=mid;
        }
    }
    cout << left << endl;
}