n,k=map(int,input().split())
A=list(map(int,input().split()))
ans=0
def make(ans):
    pre=0
    key=k
    for q in range(n):
        if pre+A[q]<ans:
            div=-(-(ans-pre-A[q])//(q+1))
            key-=div
            pre+=div*(q+1)
            if key<0:
                return 0
    return 1
for i in range(50,-1,-1):
    ans+=2**i
    if not make(ans):
        ans-=2**i
print(ans)