import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd

n,h = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
r = 0
now = 0
tot = 0
x = 0
ans = 0
for l in range(n):
    while r < n and now+(r-l+1)*b[r] <=h:
        now += (r-l+1)*b[r]
        tot += b[r]
        x += a[r]
        r += 1
    ans = max(ans, x)
    now -= tot
    x -= a[l]
    tot -= b[l]

print(ans)