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[][] dp = new int[n + 1][p + 1];
    	for (int[] arr : dp) {
    	    Arrays.fill(arr, Integer.MAX_VALUE / 2);
    	}
    	dp[0][0] = 0;
    	for (int i = 1; i <= n; i++) {
    	    int zero = sc.nextInt();
    	    int one = sc.nextInt();
    	    int two = sc.nextInt();
    	    for (int j = Math.min(p, i * 3); j >= 0; j--) {
    	        dp[i][j] = Math.min(dp[i][j], dp[i - 1][j] + zero);
    	        if (j - 1 >= 0) {
    	            dp[i][j] = Math.min(dp[i][j], dp[i - 1][j - 1] + one);
    	        }
    	        if (j - 2 >= 0) {
    	            dp[i][j] = Math.min(dp[i][j], dp[i - 1][j - 2] + two);
    	        }
    	        if (j - 3 >= 0) {
    	            dp[i][j] = Math.min(dp[i][j], dp[i - 1][j - 3] + 1);
    	        }
    	    }
    	}
    	System.out.println(dp[n][p] / (double)n);
	}
}