import sys, math
input = lambda: sys.stdin.readline()[:-1]
def MI(): return map(int, input().split())
inf = 10**18

n,k = MI()
a = list(MI())

def isok(mid):
    now = 0
    cnt = 0
    for left in range(n):
        mn = a[left] + now
        if mn<mid:
            tmp = -(-(mid-mn)//(left+1))
            cnt += tmp
            now += (left+1)*tmp
    
    if cnt<=k:
        return True
    else: return False

l,r = -1, 2*10**15
while abs(l-r)>1:
    mid = (l+r)//2
    if isok(mid): l = mid
    else: r = mid
print(l)