import sys,random,bisect
from collections import deque,defaultdict
from heapq import heapify,heappop,heappush
from itertools import permutations
from math import gcd,log

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

N,K = mi()
A = li()

def cond(x):
    add = 0
    res = 0
    for i in range(N):
        if A[i]+add < x:
            need = (x-A[i]-add+i)//(i+1)
            res += need
            add += need * (i+1)
    
    return res <= K


ok = 0
ng = 10**17
while ng-ok>1:
    mid = (ok+ng)//2
    if cond(mid):
        ok = mid
    else:
        ng = mid

print(ok)