using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Globalization;
using static System.Console;
using Pair = System.Collections.Generic.KeyValuePair<int, int>;

class Program
{
    static void Main()
    {
        var sw = new StreamWriter(OpenStandardOutput()) { AutoFlush = false };
        SetOut(sw);
        new Program().solve();
        Out.Flush();
    }
    Scanner cin = new Scanner();
    readonly int[] dd = { 0, 1, 0, -1, 0 };
    readonly int mod = 1000000007;
    readonly string alfa = "abcdefghijklmnopqrstuvwxyz";


    int N, P;
    void solve()
    {
        N = cin.nextint;
        P = cin.nextint;

        //i問解いたときの順位の合計の最小値を格納
        var dp = Enumerable.Repeat(int.MaxValue, P + 1).ToArray();
        dp[0] = 0;

        for (int i = 0; i < N; i++)
        {
            var t = cin.scanint;
            for (int j = P; j >= 0; j--)
            {
                int zero = (dp[j] == int.MaxValue) ? int.MaxValue : dp[j] + t[0];
                int one = (j - 1 < 0 || dp[j - 1] == int.MaxValue) ? int.MaxValue : dp[j - 1] + t[1];
                int two = (j - 2 < 0 || dp[j - 2] == int.MaxValue) ? int.MaxValue : dp[j - 2] + t[2];
                int three = (j - 3 < 0 || dp[j - 3] == int.MaxValue) ? int.MaxValue : dp[j - 3] + 1;
                dp[j] = Math.Min(Math.Min(zero, one), Math.Min(two, three));
            }
            //WriteLine(string.Join(" ", dp));           
        }

        WriteLine(((double)dp[P] / N).ToString("F6"));

        
    }

}

class Scanner
{
    string[] s; int i;
    char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] scan { get { return ReadLine().Split(); } }
    public int[] scanint { get { return Array.ConvertAll(scan, int.Parse); } }
    public long[] scanlong { get { return Array.ConvertAll(scan, long.Parse); } }
    public double[] scandouble { get { return Array.ConvertAll(scan, double.Parse); } }
    public string next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return next;
        }
    }
    public int nextint { get { return int.Parse(next); } }
    public long nextlong { get { return long.Parse(next); } }
    public double nextdouble { get { return double.Parse(next); } }
}