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

A_cumsum = [0] * (N + 1)
B_cumsum = [0] * (N + 1)
B_cumsum_weighted = [0] * (N + 1)

for i in range(1, N + 1):
    A_cumsum[i] = A_cumsum[i - 1] + A[i - 1]
    B_cumsum[i] = B_cumsum[i - 1] + B[i - 1]
    B_cumsum_weighted[i] = B_cumsum_weighted[i - 1] + i * B[i - 1]

max_satisfaction = 0
L = 1

for R in range(1, N + 1):
    while L <= R:
        fatigue = (B_cumsum_weighted[R] - B_cumsum_weighted[L - 1]) - (L - 1) * (B_cumsum[R] - B_cumsum[L - 1])
        if fatigue <= H:
            break
        L += 1
    if L > R:
        continue
    satisfaction = A_cumsum[R] - A_cumsum[L - 1]
    if satisfaction > max_satisfaction:
        max_satisfaction = satisfaction

print(max_satisfaction)