# 二分探索してみるか?
# 毎回の判定に時間がかかりすぎる気がする

def check(x):
    add = 0
    add_cum = 0
    for i in range(1, N+1):
        if A[i-1]+add_cum < x:
            calc = (x-A[i-1]-add_cum+(i-1))//i
            add += calc
            add_cum += calc*i
    if add <= K:
        return 1
    else:
        return 0
            
N, K = map(int, input().split())
A = list(map(int, input().split()))

#for x in range(0, 10):
#    print(x, check(x))

OK = -1
NG = 10**20
while (NG-OK)>1:
    mid = (NG+OK)//2
    if check(mid) == 1:
        OK = mid
    else:
        NG = mid
print(OK)