#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;

int main(){
    int n, k; cin >> n >> k;
    vector<ll> a(n);
    for(auto &it: a) cin >> it;

    ll ac = 0, wa = 1LL << 60;
    while(wa-ac > 1){
        ll wj = (wa+ac)/2;
        ll k1 = k;
        ll tot = 0;
        for(int i = 0; i < n; i++){
            if(wj <= a[i]+tot) continue;
            ll x = wj-(a[i]+tot);
            x = (x+i)/(i+1);
            tot += x*(i+1);
            k1 -= x;
            if(k1 < 0) break;
        }
        (k1 < 0 ? wa : ac) = wj;
    }
    cout << ac << endl;
    return 0;
}