#include <iostream>
using namespace std;
const int N = 1010;
int f[N];
int n, m;
int main()
{
    cin >> m >> n;
    for(int i = 1; i <= n; ++ i)
    {
        int v, w;
        cin >> v >> w;
        for(int j = m; j >= v; -- j)
        {
            f[j] = max(f[j], f[j - v] + w);
        }
    }
    cout << f[m] << '\n';
    return 0;
}