#include<iostream>
#include<algorithm>
using namespace std;
const int N = 105;
int n,m;
int v[N],w[N];
int dp[N][1005];
int main()
{
    cin>>m>>n;
    for(int i = 1;i<=n;i++) cin>>w[i]>>v[i];
    for(int i = 1;i<=n;i++)
    {
        for(int j = 0;j<=m;j++)
        {
            dp[i][j] = dp[i-1][j];
            if(j>=v[i]) dp[i][j] = max(dp[i][j],dp[i-1][j-w[i]]+v[i]);
        }
    }
    cout<<dp[n][m]<<endl;
}