n,h=map(int,input().split())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
rui=[0]*(n+1)
for i in range(n):
	rui[i+1]=rui[i]+b[i]

right = 0
now_manzoku = 0
now_hirou = 0
ans = 0
for left in range(n):
	while right<n:
		if right<left:
			now_hirou+=(right-left+1)*b[right]
			now_manzoku+=a[right]
			right+=1
			continue
		if now_hirou>h:break
		now_hirou+=(right-left+1)*b[right]
		now_manzoku+=a[right]
		right+=1
		if now_hirou>h:
			right-=1
			now_manzoku-=a[right]
			now_hirou-=(right-left+1)*b[right]
			break
	ans=max(ans,now_manzoku)
	now_manzoku-=a[left]
	now_hirou-=rui[right]-rui[left]
print(ans)