N,H=map(int,input().split())
A=[0]+list(map(int,input().split()))
B=[0]+list(map(int,input().split()))
cumA=[0 for _ in range(N+1)]
cumB=[0 for _ in range(N+1)]
for i in range(1,N+1):
    cumA[i]=cumA[i-1]+A[i]
    cumB[i]=cumB[i-1]+B[i]
ans=0
l=1
s=0
for r in range(1,N+1):
    s+=(r-l+1)*B[r]
    while s>H:
        s-=cumB[r]-cumB[l-1]
        l+=1
    ans=max(ans,cumA[r]-cumA[l-1])
print(ans)