N, H = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

ret = 0

suma = 0
sumb0 = 0
sumb1 = 0

l = 0

for r in range(N):
    # [l, r]
    suma += A[r]

    sumb0 += B[r]
    sumb1 += B[r] * r

    while True:
        # B[l] * 1 + B[l + 1] * 2 + ... + B[r] * (r - l + 1)
        s = sumb1 - sumb0 * (l - 1)
        if s <= H:
            break
        else:
            suma -= A[l]
            sumb0 -= B[l]
            sumb1 -= B[l] * l
            l += 1

    ret = max(ret, suma)

print(ret)