n, h = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

ab = [0] * (n + 1)
for i in range(n):
    ab[i + 1] = ab[i] + b[i]

maxv, tired, sat, r = 0, 0, 0, 0

for l in range(n):
    
    while r < n and tired + (r - l + 1) * b[r] <= h:
        tired += (r - l + 1) * b[r]
        sat += a[r]
        r += 1

    maxv = max(maxv, sat)

    if r > l:
        tired -= ab[r] - ab[l]
        sat -= a[l]

print(maxv)