n, h = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

maxv, sat, tired, r = 0, 0, 0, 0

for l in range(n):
    
    while r < n and tired + (r - l + 1) * b[r] <= h:
        tired += (r - l + 1) * b[r]  
        sat += a[r]  
        r += 1
 
    maxv = max(maxv, sat)

    if r > l:
        tired -= b[l] * (r - l)  
        sat -= a[l]
    else:
        r += 1  

print(maxv)