from itertools import accumulate
import sys


def printe(*args, end="\n", **kwargs):
    print(*args, end=end, file=sys.stderr, **kwargs)


def main():
    N, H = map(int, input().split())
    A = list(map(int, input().split()))
    B = list(map(int, input().split()))
    A_accum = list(accumulate(A))
    B_accum = list(accumulate(B, initial=0))

    max_satisfied = 0
    L = 0
    R = 0
    cur_tired = 0
    cur_satisfied = 0
    while L < N:

        if R == N:
            max_satisfied = max(max_satisfied, cur_satisfied)
            break
        if cur_tired + B[R] * (R - L + 1) <= H:
            cur_tired += B[R] * (R - L + 1)
            cur_satisfied += A[R]
            R += 1
            continue

        max_satisfied = max(max_satisfied, cur_satisfied)
        if L < R:
            cur_satisfied -= A[L]
            cur_tired -= B_accum[R] - B_accum[L]
            L += 1
        else:
            L += 1
            R += 1
        # cur_satisfied += A[R]

        # cur_tired += B[R] * (R - L)
        # R += 1
        # L += 1
    print(max_satisfied)


if __name__ == "__main__":
    main()