N,H = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
A2 = [0] + A[:]
B2 = [0] + B[:]
for i in range(1,N + 1):
    A2[i] += A2[i-1]
    B2[i] += B2[i-1]
j = 0
ans = 0
tmp = 0
for i in range(N):
    while j < N and tmp <= H:
        ans = max(ans,A2[j] - A2[i])
        #print(i,j,tmp,A2[j] - A2[i])
        j += 1
        tmp += B[j-1] * (j - i)
    tmp -= (B2[j] - B2[i])

print(ans)