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

int main( ) {
    std::ios_base::sync_with_stdio(0);
    std::cin.tie(0);

    int s, n;
    std::cin >> s >> n;

    std::vector<std::array<int, 2>> v(n + 1);
    for (int i = 0; i < n; ++i) {
        std::cin >> v[i][0] >> v[i][1];
    }

    int memo[2][s + 1];
    int* act = &memo[0][0];
    int* ant = &memo[1][0];
    for (int i = n; i >= 0; --i, std::swap(act, ant)) {
        for (int c = 0; c <= s; ++c) {
            if (i == n) {
                act[c] = 0;
            } else {
                int res = ant[c];
                if (v[i][0] <= c) {
                    res = std::max(res, v[i][1] + ant[c - v[i][0]]);
                }
                act[c] = res;
            }
        }
    }
    std::cout << ant[s];
}