T = int(input())
N = int(input())
c = list(map(int,input().split()))
v = list(map(int,input().split()))

dp = [[0] * (T+1) for _ in range(N+1)]
for i in range(N):
    for j in range(T + 1):
        if dp[i][j] > dp[i+1][j]:
            dp[i+1][j] = dp[i][j]
        value = v[i]
        now = 0
        cost = c[i]
        k = 1
        while j + cost * k <= T and value > 0:
            now += value
            dp[i+1][j+cost * k] = max(dp[i+1][j+cost * k],dp[i][j] + now)
            value = value // 2
            k += 1
print(max(dp[N]))