import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int N = sc.nextInt();
		final int P = sc.nextInt();
		
		long[] DP = new long[P + 1];
		long[] nextDP = new long[P + 1];
		
		final long INF = Long.MAX_VALUE / 2 - 1;
		for(int i = 0; i < N; i++){
			Arrays.fill(nextDP, INF);
			
			final int fst = sc.nextInt();
			final int snd = sc.nextInt();
			final int thd = sc.nextInt();
			
			for(int p = 0; p <= P; p++){
				nextDP[p] = Math.min(nextDP[p], DP[p] + fst);
			}
			for(int p = 0; p <= P - 1; p++){
				nextDP[p + 1] = Math.min(nextDP[p + 1], DP[p] + snd);
			}
			for(int p = 0; p <= P - 2; p++){
				nextDP[p + 2] = Math.min(nextDP[p + 2], DP[p] + thd);
			}
			for(int p = 0; p <= P - 3; p++){
				nextDP[p + 3] = Math.min(nextDP[p + 3], DP[p] + 1);
			}
			
			//System.out.println(Arrays.toString(nextDP));
			{
				long[] tmp = DP;
				DP = nextDP;
				nextDP = tmp;
			}
		}
		
		
		System.out.printf("%.08f\n", DP[P] / (double)(N));
	}
}