#include<iostream>
#include<string>
#include<cctype>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<vector>
#include<algorithm>
#include<map>
#include<set>
#include<iomanip>
using namespace std;
#define LL long long
const int N = 1e7+10;
const int INF = 0x3f3f3f3f;
long long dp[N],n,m,w,v; 
int main(){
	//freopen("","r",stdin);
	//freopen("","w",stdout);
	cin>>m>>n;
	for(int i=1;i<=n;i++){
		cin>>v>>w;
		for(int j=w;j<=m;j++){
			dp[j]=max(dp[j],dp[j-w]+v);
		}
	}
	cout<<dp[m]<<endl;
	return 0;
}