n,h=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))

accB=[0]*(n+1)
for i in range(n):
    accB[i+1]=accB[i]+B[i]
    
ans=0
r=0
tired=0
satisfied=0
for l in range(n):
    while r<n and tired+(r-l+1)*B[r]<=h:
        tired+=(r-l+1)*B[r]
        satisfied+=A[r]
        r+=1
        
    ans=max(ans,satisfied)
    tired-=accB[r]-accB[l]
    satisfied-=A[l]
    
print(ans)