import sys
input = sys.stdin.readline

N,K = map(int,input().split())
A = list(map(int,input().split()))

OK=0
NG=10**18

while NG>OK+1:
    mid=(OK+NG)//2
    c=0
    p=0

    for i in range(N):
        if A[i]+c<mid:
            u=mid-A[i]-c
            x=i+1

            k=(u+x-1)//x
            p+=k
            c+=k*x
    if p<=K:
        OK=mid
    else:
        NG=mid
print(OK)