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

public class Main {
    static HashMap<Integer, Integer>[] dp;
    static int[][] contests;
    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]);
        dp = new HashMap[n + 1];
        contests = new int[n + 1][3];
        for (int i = 1; i <= n; i++) {
            String[] line = br.readLine().split(" ", 3);
            for (int j = 0; j < 3; j++) {
                contests[i][j] = Integer.parseInt(line[j]);
            }
            dp[i] = new HashMap<Integer, Integer>();
        }
        System.out.println(dfw(n, 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].containsKey(count)) {
            return dp[idx].get(count);
        }
        int ans = Integer.MAX_VALUE;
        for (int i = 0; i < 3; i++) {
            if (count - i > (idx - 1) * 3) {
                continue;
            }
            ans = Math.min(ans, dfw(idx - 1, count - i) + contests[idx][i]);
        }
        ans = Math.min(ans, dfw(idx - 1, count - 3) + 1);
        dp[idx].put(count, ans);
        return ans;
    }
}