#include <iostream>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
int main(){
	ll t, m;
	cin >> t >> m;
	vector<pair<ll, ll>> arr(m);
	vector<ll> dp(t + 1, 0);
	for (int i = 0; i < m; i++) {
        cin >> arr[i].first >> arr[i].second;
    }
	//״̬-> dp[i] = max(dp[i - time[i]] + value[i])
	for(int i = 1; i < t + 1; i++){
		for(int j = 0; j < m; j++){
			if(i - arr[j].first >= 0) dp[i] = max(dp[i], dp[i - arr[j].first] + arr[j].second);
		}
	}
	cout << dp[t] << endl;
	return 0;
}