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

right, ans, SUM, satisfaction, sumB = 0, 0, 0, 0, 0
for left in range(N):
    while right < N and SUM+(right-left+1)*B[right] <= H:
        SUM += (right-left+1)*B[right]
        sumB += B[right]
        satisfaction += A[right]
        right += 1
    ans = max(ans, satisfaction)
    if left == right:
        right += 1
        continue
    SUM -= sumB
    sumB -= B[left]
    satisfaction -= A[left]

print(ans)