import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

n,k = na()
a = na()
ok = 0
ng = 10**20

while abs(ok - ng)>1:
    d = ok+ng>>1
    s = 0
    res = 0
    for i in range(n):
        x = d - s - a[i]
        if x >= 0:
            s += (x + i)//(i+1) * (i+1)
            res += (x + i)//(i+1)
    if res <= k:
        ok = d
    else:
        ng = d

print(ok)