#include<bits/stdc++.h>
using namespace std;

int main() {
    int n, m;
    cin >> n >> m;
    int v[m], p[m];
    for (int i = 0; i < m; i++) {
        cin >> v[i] >> p[i];
    }
    int money[m];
    for (int i = 0; i < m; i++) {
        money[i] = v[i] * p[i];
    }
    int dp[26][30005];
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - v[j]] + money[i]);
        }
    }
    cout << dp[m][n] << endl;
    return 0;
}

全部$\color{white}\colorbox{DarkOrchid}{RE}$了