n, k = map(int, input().split())
A = list(map(int, input().split()))

left, right = -1, 10**15
while right - left > 1:
    mid = (left + right) // 2
    res = 0
    cnt = 0
    for i in range(n):
        ai = A[i] + res
        if ai >= mid:
            continue
        tmp = (mid - ai + i) // (i + 1)
        cnt += tmp
        res += tmp * (i + 1)
    if cnt <= k:
        left = mid
    else:
        right = mid
print(left)