#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int T, M;
    cin >> T >> M;

    vector<int> times(M);
    vector<int> values(M);

    for (int i = 0; i < M; ++i) {
        cin >> times[i] >> values[i];
    }

    vector<int> dp(T + 1, 0);

    for (int i = 0; i < M; ++i) {
        for (int j = T; j >= times[i]; --j) {
            dp[j] = max(dp[j], dp[j - times[i]] + values[i]);
        }
    }

    cout << dp[T] << endl;

    return 0;
}