#############################################################

import sys
sys.setrecursionlimit(10**7)

from heapq import heappop,heappush
from collections import deque,defaultdict,Counter
from bisect import bisect_left, bisect_right
from itertools import product,combinations,permutations

ipt = sys.stdin.readline

def iin():
    return int(ipt())
def lmin():
    return list(map(int,ipt().split()))

MOD = 998244353
#############################################################

N,H = lmin()
A = lmin()
B = lmin()

SA = [0]
for a in A:
    SA.append(SA[-1]+a)
SB = [0]
SSB = [0]
for i,b in enumerate(B):
    SB.append(SB[-1]+b*(i+1))
    SSB.append(SSB[-1]+b)

ans = 0
for i in range(N):
    ok = i
    ng = N+1
    while ng-ok > 1:
        cen = (ok+ng)//2
        if SB[cen]-SB[i]-(SSB[cen]-SSB[i])*i <= H:
            ok = cen
        else:
            ng = cen
    ans = max(ans,SA[ok]-SA[i])
print(ans)