import sys
input = sys.stdin.readline
N, H = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
SA = [0]
for a in A:
    SA.append(SA[-1]+a)
SB = [0]
for b in B:
    SB.append(SB[-1]+b)
SH = [0]
for i, b in enumerate(B):
    SH.append(SH[-1]+(i+1)*b)
ans = 0
for i in range(N):
    l = i-1
    r = N
    while r-l>1:
        mid = (l+r)//2
        tmp = SH[mid+1]-SH[i]-(SB[mid+1]-SB[i])*i
        if tmp<=H:
            l = mid
        else:
            r = mid
    ans = max(ans, SA[l+1]-SA[i])
print(ans)