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; } }