# 後ろから累積和してみたが高速計算できない
# しゃくとり法だった, ABC032C利用

N, H = map(int, input().split())
A = [0]+list(map(int, input().split()))
B = [0]+list(map(int, input().split()))

A_cumu = []
temp = 0
for a in A:
    temp += a
    A_cumu.append(temp)

B_cumu = []
temp = 0
for b in B:
    temp += b
    B_cumu.append(temp)

#print('A', A)
#print('A_cumu', A_cumu)
#print('B', B)
#print('B_cumu', B_cumu)

right = 1
left = 1
ans = 0
calc = 0
while left < N+1 and right < N+1:
    while right < N+1:
        #print('right', right, '(right+1-left)', (right+1-left))
        if calc+B[right]*(right+1-left) <= H:
            calc += B[right]*(right+1-left)
            ans = max(ans, A_cumu[right]-A_cumu[left-1])
            #print('(right+1-left)', (right+1-left), 'calc', calc, 'ans', ans)
            right += 1
        else:
            break
    #print('前', 'left', left, 'right', right, 'calc', calc, 'ans', ans)
    
    calc -= (B_cumu[right-1]-B_cumu[left-1])
    left += 1
    if left >= right:
        right = left 
        calc = 0

    #print('後', 'left', left, 'right', right, 'calc', calc, 'ans', ans)

print(ans)