N, H = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
Bc = [0] * (N + 1)
for i in range(N):
    Bc[i + 1] = Bc[i] + B[i]
    
from collections import *
Q = deque()
v, ans, temp = 0, 0, 0
for i in range(N):
    Q.append(i)
    v += len(Q) * B[i]
    temp += A[i]
    while v > H:
        ind = Q.popleft()
        v -= Bc[i + 1] - Bc[ind]
        temp -= A[ind]
    ans = max(ans, temp)
    
print(ans)