def isok(r):
    tmp=B[r]-B[l-1]-(B2[r]-B2[l-1])*l
    if tmp<=H:
        return True
    return False

N,H=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
for i in range(N-1):
    A[i+1]+=A[i]
A+=[0]
B2=B[::]
B=[B[i]*(i+1) for i in range(N)]
for i in range(N-1):
    B[i+1]+=B[i]
    B2[i+1]+=B2[i]
B2+=[0]
B+=[0]
ans=0
for l in range(N):
    left,right=l-1,N
    while right-left>1:
        mid=(right+left)//2
        if isok(mid):
            left=mid
        else:
            right=mid
    ans=max(A[left]-A[l-1],ans)
    #print(l,left,A[left]-A[l-1],B[left]-B[l-1]-(B2[left]-B2[l-1])*l)
print(ans)