#include<iostream>
#include<cstdio>
#include<algorithm>
#define MAXN 250000
#define MAXN1 40000
using namespace std;
int n,V;
int v[MAXN],w[MAXN1],f[MAXN];
int main(){
	freopen("medic.in","r",stdin);
	freopen("medic.out","w",stdout);
	scanf("%d%d",&V,&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=V;j>=v[i];j--){
           int temp=f[j-v[i]]+w[i];
           if(temp>f[j]) f[j]=temp;
       }
    printf("%d",f[V]);
    //printf("%fMB",(float)(sizeof(v)+sizeof(w)+sizeof(f))/1024/1024);
    fclose(stdin);
    fclose(stdout);
    return 0;
}