N,H = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))

ruisekiwa=[0]*(N+1)
for i in range(N):
    ruisekiwa[i+1]=ruisekiwa[i]+B[i]

left=0
right=0
now=0
ans=0
score=0
for i in range(N):
    if now+B[i]*(i+1-left)<=H:
        score+=A[i]
        now+=B[i]*(i+1-left)
    else:
        now-=ruisekiwa[i]-ruisekiwa[left]
        score-=A[left]
        left+=1
        if now+B[i]*(i+1-left)<=H:
            score+=A[i]
            now+=B[i]*(i+1-left)
        else:
            now-=ruisekiwa[i]-ruisekiwa[left]
            score-=A[left]
            left+=1
    ans=max(ans,score)
print(ans)