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

t = [0 for _ in range(n+1)]
for i in range(n):
    t[i+1] = t[i] + b[i]

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)

    tired -= t[r] - t[l] 
    sat -= a[l]
        
print(maxv)