n, h = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
cum = [0]
for b in B:
    cum.append(cum[-1] + b)

ans = 0
r = 0
tot = 0
ca = 0
for l in range(n):
    while r < n:
        ntot = tot + B[r] * (r - l + 1)
        if ntot > h:
            break
        tot = ntot
        ca += A[r]
        r += 1
    ans = max(ans, ca)
    ca -= A[l]
    tot -= cum[r] - cum[l]

print(ans)