N,K=map(int,input().split())
A=[int(i) for i in input().split()]

def solve(N,K,A,X):
    '''
    長さNの列Aに対して操作K回以下で最小値をX以上にできるかどうか
    '''
    B=[A[i] for i in range(N)]
    geta=0
    for i in range(N):
        B[i]+=geta
        if B[i]<X:
            tmp=(X-B[i]+i)//(i+1)
            K-=tmp
            if K<0:
                return False
            geta+=(i+1)*tmp
    if K>=0:
        return True
    else:
        return False

low=0
high=10**15
while(high-low>1):
    mid=(high+low)//2
    if solve(N,K,A,mid):
        low=mid
    else:
        high=mid
print(low)