// yukicoder: No.37 遊園地のアトラクション
// 2019.7.1 bal4u

#include <stdio.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() {   // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

int N, T;
int c[16];
int sc[16][10], sv[16][10], sz[16];
int dp[16][11005];

inline static int MAX(int a, int b) { if (a < b) a = b; return a; }

int main()
{
	int i, j, k, t;

	T = in(), N = in();
	for (i = 1; i <= N; i++) c[i] = in();
	for (i = 1; i <= N; i++) {
		k = in();
		sc[i][0] = sv[i][0] = 0;
		for (j = 1; k; j++) {
			sc[i][j] = sc[i][j-1] + c[i];
			sv[i][j] = sv[i][j-1] + k;
			k >>= 1;
		}
		sz[i] = j;
	}

	dp[0][0] = 1;
	for (i = 1; i <= N; i++) {
		for (j = sz[i]-1; j >= 0; j--) {
			for (t = T; t >= 0; t--) if (dp[i-1][t]) {
				dp[i][t+sc[i][j]] = MAX(dp[i][t+sc[i][j]], dp[i-1][t]+sv[i][j]);
			}
		}
	}
	
	k = 0;
	for (t = T; t >= 0; t--) if (dp[N][t] > k) k = dp[N][t];
	printf("%d\n", k-1);
	return 0;
}