import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class HiringEmployees_lewin {
    public static ArrayList<Integer>[] child;
    public static int[] s, p, r, sz;
    public static int n, k;

    public static void main (String[] args) {
        Scanner in = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out, true);
        
        k = in.nextInt()+1; // include the CEO
        n = in.nextInt();
        s = new int[n+1];
        p = new int[n+1];
        r = new int[n+1];

        child = new ArrayList[n+1];
        for (int i = 0; i <= n; i++) child[i] = new ArrayList<>();
        for (int i = 1; i <= n; i++) {
            s[i] = in.nextInt();
            p[i] = in.nextInt();
            r[i] = in.nextInt();
            child[r[i]].add(i);
        }

        sz = new int[n+1];
        for (int i = n; i >= 0; i--) {
            sz[i] = 1;
            for (int next : child[i])
                sz[i] += sz[next];
        }
        
        double lo = 0, hi = 10000;
        for (int iter = 0; iter < 40; iter++) {
            double mid = (lo+hi) / 2.;
            if (can(mid)) lo = mid;
            else hi = mid;
        }

        out.printf("%.3f\n", lo);
        System.exit(0);
    }
    
    public static boolean can(double ratio) {
        double[][] dp = new double[n+1][];
        for (int i = n; i >= 0; i--) {
            int cs = Math.min(k, sz[i]);
            dp[i] = new double[cs+1];
            Arrays.fill(dp[i], -(1l<<60));
            int last = 1;
            dp[i][1] = p[i] - ratio * s[i];
            for (int next : child[i]) {
                for (int y = Math.min(last, cs); y >= 0; y--) {
                    for (int x = 0; x+y <= cs && x < dp[next].length; x++) {
                        dp[i][x+y] = Math.max(dp[i][x+y], dp[i][y] + dp[next][x]);
                    }
                }
                last += dp[next].length;
            }
            dp[i][0] = 0;
        }
        return dp[0][k] >= 0;
    }
}