#include<bits/stdc++.h>
using namespace std;
int t,m,dp[1005][1005],a[1005],b[1005];
int main(){
    cin>>t>>m;

    for(int i=1;i<=m;i++) cin>>a[i]>>b[i];

    for(int i=1;i<=m;i++){
        for(int j=1;j<=t;j++){
            if(a[i]<=j) dp[i][j]=max(dp[i-1][j],dp[i-1][j-a[i]]+b[i]);
            else dp[i][j]=dp[i-1][j];
            //cout << dp[i][j] << " ";
        }
        //cout<<endl;

    }
    cout<<dp[m][t];
    return 0;
}