#include <iostream>
#include <cstdio>
using namespace std;
int dp[101][1001],n,m,v[101],w[101],ans;
int main(){
	freopen("medic.in","r",stdin);
	freopen("medic.out","w",stdout);
	scanf("%d %d",&m,&n);
	for(int i=1;i<=n;i++){
		scanf("%d %d",v+i,w+i);
	}
	for(int i=1;i<=n;i++){
		for(int j=1;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-v[i]]+w[i]);
			if(i==n)ans=max(ans,dp[i][j]);
		}
	}
	printf("%d\n",ans);
	return 0; 
}