import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd

n,k = map(int,input().split())
a =[0] + list(map(int,input().split()))

l = 0
r = 10**18
while r-l > 1:
  m = (r+l)//2
  cnt = 0
  now = 0
  for i in range(1, n+1):
    if a[i] + now < m:
      dif = m - (a[i] + now)
      tmp = (dif+i-1)//i
      cnt += tmp
      now += tmp * i
  if cnt <= k:
    l = m
  else:
    r = m
  
print(l)