# WA 解法、不等号のミス
n,h = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

suma = [0]
for i in range(n):
    suma.append(suma[-1]+a[i])

sumb = [0]
for i in range(n):
    sumb.append(sumb[-1]+b[i])

now = 0
r = 0
ans = 0
for l in range(n):
    if l!=0:
        now -= sumb[r] - sumb[l-1]
    # 本来は <= の部分を < にした
    while r<n and now + (r-l+1)*b[r] < h:
        now += (r-l+1) * b[r]
        r += 1
    ans = max(ans, suma[r] - suma[l])

print(ans)