#include<iostream>
#include<fstream>
#include<vector>
#define DM 10003
using namespace std;
fstream fin("rucsac.in",ios::in),fout("rucsac.out",ios::out);
vector <pair<int,int> > v;
int x[DM][DM];
int main()
{
    int i,n,g,a,b,j;
    v.push_back(make_pair(a,b));
    fin>>n>>g;
    for(i=1;i<=g;i++)
    {
        fin>>a>>b;
        v.push_back(make_pair(a,b));
    }
    for(i=1;i<=g;i++)
    {
        for(j=1;j<=n;j++)
        {
            x[i][j]=x[i][j-1];
            if(i-v[j].first>=0)
            x[i][j]=max(x[i][j],x[i-v[j].first][j-1]+v[j].second);
        }
    }
    cout<<x[g][n];
    return 0;
}