import java.util.*;
import java.io.*;

public class Main {
    static int[][] scores;
    static int[][] dp;
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] first = br.readLine().split(" ", 2);
        int n = Integer.parseInt(first[0]);
        int p = Integer.parseInt(first[1]);
        scores = new int[n][3];
        for (int i = 0; i < n; i++) {
            String[] line = br.readLine().split(" ", 3);
            for (int j = 0; j < 3; j++) {
                scores[i][j] = Integer.parseInt(line[j]);
            }
        }
        dp = new int[n][];
        for (int i = 0; i < n; i++) {
            dp[i] = new int[Math.min((i + 1) * 3 + 1, p + 1)];
        }
        System.out.println(dfw(n - 1, p) / (double)n);
    }
    
    static int dfw(int idx, int count) {
        if (count < 0) {
            return Integer.MAX_VALUE / 2;
        }
        if (idx < 0) {
            return 0;
        }
        if (dp[idx][count] != 0) {
            return dp[idx][count];
        }
        int min = Integer.MAX_VALUE / 2;
        if (idx * 3 >= count) {
            min = Math.min(min, dfw(idx - 1, count) + scores[idx][0]);
        }
        if (idx * 3 >= count - 1) {
            min = Math.min(min, dfw(idx - 1, count - 1) + scores[idx][1]);
        }
        if (idx * 3 >= count - 2) {
            min = Math.min(min, dfw(idx - 1, count - 2) + scores[idx][2]);
        }
        if (idx * 3 >= count - 3) {
            min = Math.min(min, dfw(idx - 1, count - 3) + 1);
        }
        dp[idx][count] = min;
        return min;
    }
}