using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, k) = (c[0], c[1]);
        var a = NList;
        var ok = 0L;
        var ng = 1_000_000_000_000_000;
        while (ng - ok > 1)
        {
            var mid = (ok + ng) / 2;
            var cnt = 0L;
            var add = 0L;
            for (var i = 0; i < n; ++i)
            {
                if (a[i] + add < mid)
                {
                    var sub = (mid - add - a[i] + i) / (i + 1);
                    cnt += sub;
                    add += sub * (i + 1);
                }
            }
            if (cnt > k) ng = mid;
            else ok = mid;
        }
        WriteLine(ok);
    }
}