#include <bits/stdc++.h>
using namespace std;
long long i, j, m, n, w[1005], v[1005], dp[10000005];

int main(){
	ios::sync_with_stdio(0);
	cin >> m >> n;
	for (i = 1; i <= n; i++) cin >> w[i] >> v[i];
	for (i = 1; i <= n; i++)
		for (j = w[i]; j <= m; j++) dp[j] = max(dp[j], dp[j - w[i]] + v[i]);
	cout << dp[m] << endl;
    return 0;
}