#include<iostream>
using namespace std;
const int N = 1010;
int f[N];
int main() {
int t, m;
cin >> t >> m;
for (int i = 1; i <= m; i++) {
int tt, ww;
cin >> tt >> ww;
for (int j = t; j >= tt; j--)
f[j] = max(f[j], f[j - tt] + ww);
}
cout << f[t] << endl;
return 0;
}