#include <bits/stdc++.h>
using namespace std;
int n, m, w[1010], c[1010], dp[110][1010];
int main(){
	cin >> m >> n;
	for(int i = 1 ; i <= n ; i++){
		cin >> w[i] >> c[i];
	}
	for(int i = 1 ; i <= n ; i++){
		for(int j = 1 ; j <= m ; j++){
			if(w[i] > j) dp[i][j] = dp[i - 1][j];
			else dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - w[i]] + c[i]);
		}
	}
	cout << dp[n][m];
	return 0;
}