#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <atcoder/modint>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;

using Modint = atcoder::static_modint<1000000007>;

int main(){
    i64 N, K; cin >> N >> K;
    vector<i64> A(N); rep(i,N) cin >> A[i];
    i64 l = 0, r = INF;
    while(l+1 < r){
        i64 m = (l+r)/2;
        i64 q = 0;
        i64 w = 0;
        rep(i,N) if(A[i] + w < m){
            i64 t = (m - (A[i] + w) - 1) / (i+1) + 1;
            q += t; w += t * (i+1);
        }
        if(q <= K){ l = m; } else { r = m; }
    }
    cout << l << endl;
    return 0;
}



struct ios_do_not_sync{
    ios_do_not_sync(){
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} ios_do_not_sync_instance;