#include<iostream>
using namespace std;
int main()
{
    int T,M,book[1001][1001];
    int w[1001],v[1001];
    cin>>T>>M;
    for(int i=1;i<=M;i++)
    {
        cin>>w[i]>>v[i];
    }
    for(int i=1;i<=M;i++)
    {
        for(int j=T;j>=0;j--)
        {
            if(j<=w[i])
                book[i][j]=book[i-1][j];
            else
            {
                book[i][j]=max(book[i-1][j],book[i-1][j-w[i]]+v[i]);
            }
            
        }
    }
    cout<<book[M][T]<<endl;
}