import java.math.BigInteger;

import java.util.Scanner;

public class Main {

public static void main(String[] args) {

Scanner sc=new Scanner(System.in);

int m=sc.nextInt();

int n=sc.nextInt();

int s[]=new int[n+1];

int v[]=new int[n+1];

for(int i=1;i<=n;i++){

s[i]=sc.nextInt();

v[i]=sc.nextInt(); }

int arr[][]=new int[n+1][m+1];

for(int i=1;i<=n;i++){

for(int j=1;j<=m;j++){

if(s[i]>j)arr[i][j]=arr[i-1][j];

else arr[i][j]=Math.max(arr[i-1][j],arr[i-1][j- s[i]]+v[i]);

}

}

System.out.printf("%d",arr[n][m]);

}

}