n, k = map(int, input().split())
a = list(map(int, input().split()))
l = -1
r = a[0] + k + 1
while r - l > 1:
    c = (l + r) // 2
    cnt = 0
    add = 0
    for i, x in enumerate(a, 1):
        x += add
        if c > x:
            v = (c - x + i - 1) // i
            cnt += v
            add += v * i
    if cnt <= k:
        l = c
    else:
        r = c
print(l)