import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();
        int m = sc.nextInt();
        int[] dp = new int[t + 1];
        while (m-- != 0) {
            int weight = sc.nextInt();
            int value = sc.nextInt();
            for (int i = t; i >= weight; i--) {
                dp[i] = Math.max(dp[i], dp[i - weight] + value);
            }
        }
        System.out.println(dp[t]);
    }
}