#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

ll N, K;
vector<ll> A;

bool solve(ll X){
    ll S=0, cnt=0;
    for (ll i=1; i<=N; i++){
        if (A[i]+S < X){
            cnt += (X-(A[i]+S)+i-1) / i;
            S +=  (X-(A[i]+S)+i-1) / i * i;
        }
    }
    return cnt <= K;
}

int main(){

    cin >> N >> K;
    A.resize(N+1);
    for (int i=0; i<N; i++) cin >> A[i+1];

    ll l=0, r=1e15, c;
    while(r-l>1){
        c = (l+r)/2;
        if (solve(c)) l=c;
        else r=c;
    }

    cout << l << endl;

    return 0;
}