import java.util.*;

public class Main {
    static final int N = 1010, M = 110;
    static int[][] f = new int[N][N];
    static int[][] a = new int[M][2];
    static int n, m;

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String[] str = sc.nextLine().split(" ");
        n = Integer.parseInt(str[0]); m = Integer.parseInt(str[1]);

        for (int i = 1; i <= m; i++) {
            str = sc.nextLine().split(" ");
            int t = Integer.parseInt(str[0]), w = Integer.parseInt(str[1]);
            a[i] = new int[] {t, w};
        }


        for (int i = 1; i <= m; i++)
            for (int j = 1; j <= n; j++) {
                f[i][j] = f[i - 1][j];
                if (a[i][0] <= j) f[i][j] = Math.max(f[i][j], f[i - 1][j - a[i][0]] + a[i][1]);
            }

        System.out.println(f[m][n]);
    }
}