/*

TASK:inflate

LANG:C++

URL:

*/

#include <iostream>

#include <algorithm>

#include <cstdio>

#include <cstring>

#define ll long long

#define N 10005

int m,n,w[N],p[N],dp[N];

using namespace std;

int main() {

    freopen("inflate.in","r",stdin);

    freopen("inflate.out","w",stdout);

    scanf("%d%d",&m,&n);

    for(int i=;i<=n;i++)

        scanf("%d%d",&p[i],&w[i]);

    for(int i=;i<=n;i++)

    for(int j=w[i];j<=m;j++)

        if(dp[j-w[i]]+p[i]>dp[j])

            dp[j]=dp[j-w[i]]+p[i];

    int ans=;

    for(int i=;i<=m;i++)

    if(dp[i]>ans)ans=dp[i];

    printf("%d\n",ans);

    return ;

}