N,H = map(int,input().split())
A = [0]+list(map(int,input().split()))
B = [0]+list(map(int,input().split()))
cumA = [0]*(N+1)
cumB = [0]*(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
hirou = 0
r = 0
for l in range(1,N+1):
    hirou -= (r-l+2)*B[l-1]
    while hirou<=H:
        r += 1
        if r>N:break
        hirou += cumB[r]-cumB[l-1]
    if r>N:
        r -= 1
    if hirou>H:
        hirou -= cumB[r]-cumB[l-1]
        r -= 1
    ans = max(ans,cumA[r]-cumA[l-1])
print(ans)