taxi

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef pair<int, int> pi;
typedef long long ll;


int main()
{
    int n, m; cin >> n >> m;

    vector<ll> one, two;

    for(int i =0; i < m; i++){
        int c;
        ll p; cin >> c >> p;
        if(c == 1){
            one.push_back(p);
        }else{
            two.push_back(p);
        }
    }

    sort(one.begin(), one.end());
    reverse(one.begin(), one.end());

    sort(two.begin(), two.end());
    reverse(two.begin(), two.end());

    ll ans = 0;
    int i = 0, j = 0; // i para one, j para two

    if(n & 1){

        if(two.size() > 0 && one.size() > 0){
            ll act = two[0] + one[0];
            ll nxt = 0;
            int co = 0;
            for(int x = 0; x <= 2 && x < one.size(); x++){
                nxt += one[x];
                co++;
            }

            if(nxt > act){
                i = min(3, (int)one.size());
                n -= co;
                ans += nxt;
            }else{
                i = 1;
                j = 1;
                ans += act;
                n -= 2;
            }
        }
    }
   // cout << ans << " " << n << " " << i << " " << j << endl;
    while(n > 0){
        bool taken = false;

        if(two.size() > j && n >= 2){
            ll act = two[j];
            int k;
            ll nxt = 0;
            int co = 0;
            for(k = i; k <= i + 1 && k < one.size(); k++){
                nxt += one[k];
                co++;
            }

            if(nxt > act){
                // los (dos primeros o uno solo) son mejor, que este solo de uno...
                ans += nxt;
                i = k;
                taken = true;
                n -= co;

            }else{
                ans += act;
                j++;
                taken = true;
                n -= 2;
            }
        }else{
            if(one.size() > i){
                ans += one[i];
                i++;
                taken = true;
                n--;
            }
        }

        if(!taken) break;
    }
    cout << ans << endl;
    return 0;
}