#include<bits/stdc++.h>
using namespace std;
const int T=1007;
const int M=107;
const int INF=(1<<30)-3;
int t,m;
int tim[M],v[M];
int f[M][T];
int main(){
	cin>>t>>m;
	for(int i=1;i<=m;i++){
	    cin>>tim[i]>>v[i];
	    for(int j=1;j<=t;j++)
	    if(j>=tim[i])
	    	f[i][j]=max(f[i-1][j],f[i-1][j-tim[i]]+v[i]);
	}
	cout<<f[m][t];
    return 0;	
}