#include <iostream>

using namespace std;

const int N = 105;
const int T = 1010;
int t, n, v[N], w[N], f[N][T];

int main() {
    cin >> t >> n;
    for (int i = 1 ; i <= n ; i ++) {
        cin >> v[i] >> w[i];
    }
    for (int i = 1 ; i <= n ; i ++) {
        for (int j = 1; j <= t ; j ++) {
            f[i][j] = f[i - 1][j];
            if (j >= v[i]) f[i][j] = max(f[i][j], f[i - 1][j - v[i]] + w[i]);
        }
    }

    cout << f[n][t] << endl;
    return 0;
}