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[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[P + 1];
    dp[0] = a[0];
    if(1 < P + 1) dp[1] = b[0];
    if(2 < P + 1) dp[2] = c[0];
    if(3 < P + 1) dp[3] = 1;
    int[] arr = dp.clone();
    for(int i = 1; i < N; i++) {
      for(int j = 0; j < P + 1; j++) {
        int min = Integer.MAX_VALUE;
        if(arr[j] != 0) min = Math.min(min, a[i] + arr[j]);
        if(j >= 1 && arr[j - 1] != 0) min = Math.min(min, b[i] + arr[j - 1]);
        if(j >= 2 && arr[j - 2] != 0) min = Math.min(min, c[i] + arr[j - 2]);
        if(j >= 3 && arr[j - 3] != 0) min = Math.min(min, 1 + arr[j - 3]);
        if(min == Integer.MAX_VALUE) min = 0;
        dp[j] = min;
      }
      arr = dp.clone();
    }
    System.out.println((double)dp[P] / (double)N);
  }
}