from itertools import accumulate

N, H = map(int, input().split())
A = [int(x) for x in input().split()]
B = [int(x) for x in input().split()]

A_wa = [0] + [*accumulate(A)]
B_wa = [0] + [*accumulate(B)]

r = 0
cost = 0
cands = []
for l in range(N+1):
   if r < l:
      r = l
      cost = 0
   while r < N and cost + (r-l+1) * B[r] <= H:
      cost += (r-l+1) * B[r]
      r += 1
   cands.append(A_wa[r] - A_wa[l])
   cost -= (B_wa[r] - B_wa[l])

print(max(cands))