# include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int M = 20;
const int N = 10010;
ll T, n;
ll c[M], h[M];
ll dp[M][N];

int main()
{
	scanf("%lld%lld", &T, &n);
	for (int i = 1; i <= n; i++) scanf("%lld", &c[i]);
	for (int i = 1; i <= n; i++) scanf("%lld", &h[i]);
	for (int i = 1; i <= n; i++)
	{
		for (int j = 0; j <= T; j++)
		{
			ll piou, fan;
			piou = h[i];
			fan = 0;
			dp[i][j] = dp[i - 1][j];
			for (int k = 1; k <= log2(h[i]) + 1; k++)
			{
				fan += piou;
				if (j >= k * c[i]) dp[i][j] = max(dp[i][j], dp[i - 1][j - k * c[i]] + fan);
				piou /= 2;
			}
		}
	}
	ll ans;
	ans = 0;
	for (int i = 0; i <= T; i++) ans = max(ans, dp[n][i]);
	printf("%lld\n", ans);
	return 0;
}