#include<bits/stdc++.h>
using namespace std;
int dp[100001];
int t[10001],v[10001];
int main(){
	int T,M,i,j;
	cin>>T>>M;
	for(i=1;i<=M;i++){
		cin>>t[i]>>v[i];
	}
	for(i=1;i<=M;i++){
		for(j=t[i];j<=T;j++){
			dp[j] = max(dp[j],dp[j-t[i]]+v[i]);
		}
	}
	cout<<dp[T];

	return 0;
}

/**************************************************************
	Problem: 1780
	User: admin
	Language: C++
	Result: Accepted
	Time:67 ms
	Memory:2540 kb
****************************************************************/