import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int P = sc.nextInt();
    int[] a = new int[N];
    int[] b = new int[N];
    int[] c = new int[N];
    for(int i = 0; i < N; i++) {
      a[i] = sc.nextInt();
      b[i] = sc.nextInt();
      c[i] = sc.nextInt();
    }
    // dp[i][j]はコンテストiまでで正解数がちょうどj問の場合の順位の和の最小値(有り得ない場合は0とする)
    int[][] dp = new int[N][P + 1];
    dp[0][0] = a[0];
    dp[0][1] = b[0];
    dp[0][2] = c[0];
    dp[0][3] = 1;
    for(int i = 1; i < N; i++) {
      for(int j = 0; j < P + 1; j++) {
        int min = Integer.MAX_VALUE;
        if(dp[i - 1][j] != 0) min = Math.min(min, a[i] + dp[i - 1][j]);
        if(j >= 1 && dp[i - 1][j - 1] != 0) min = Math.min(min, b[i] + dp[i - 1][j - 1]);
        if(j >= 2 && dp[i - 1][j - 2] != 0) min = Math.min(min, c[i] + dp[i - 1][j - 2]);
        if(j >= 3 && dp[i - 1][j - 3] != 0) min = Math.min(min, 1 + dp[i - 1][j - 3]);
        if(min == Integer.MAX_VALUE) min = 0;
        dp[i][j] = min;
      }
    }
    System.out.println((double)dp[N - 1][P] / (double)N);
  }
}