#include <bits/stdc++.h>
using namespace std;
int n, t;
int dp[100000];
int maxl = 0;
int main() {
    cin >> t >> n;
    for (int i = 0; i < n; i++) {
        int a, b;
        cin >> a >> b;
        for (int j = t; j >= a; j--) {
            dp[j] = max(dp[j], dp[j - a] + b);
            maxl = max(maxl, dp[j]);
        }
    }
    cout << maxl;
    return 0;
}