package no472;

import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {
	public static int INF = (int) 1e9;
	public static void main(String[] args) {
		ValidatingScanner sc = new ValidatingScanner(true);
		int n = sc.readInt(1, 5000);
		sc.readSpace();
		int p = sc.readInt(0, 3*n);
		sc.readEoln();
		int[][] rank = new int[n][4];
		for(int i=0;i<n;i++) {
			int a = sc.readInt(2, 100000);
			sc.readSpace();
			int b = sc.readInt(2, a-1);
			sc.readSpace();
			int c = sc.readInt(2, b-1);
			sc.readEoln();
			rank[i][0] = a;
			rank[i][1] = b;
			rank[i][2] = c;
			rank[i][3] = 1;
		}
		sc.readEof();
		
		int[] dp = new int[p+1];
		Arrays.fill(dp, INF);
		dp[0] = 0;
		for(int i=0;i<n;i++) {
			for(int j=p;j>=0;j--) {
				int next = INF;
				for(int k=0;k<=3;k++) {
					if (j - k < 0) {
						break;
					}
					next = Math.min(next, dp[j-k] + rank[i][k]);
				}
				dp[j] = next;
			}
//			System.out.println(Arrays.toString(dp));
		}
		System.out.println(String.format("%.6f", (double) dp[p] / n));
	}
}
class ValidatingScanner {
	boolean strictEoln = false;
	public static final String EOLN = "\n";
	
	private final InputStream in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;

	public ValidatingScanner(boolean strictEoln) {
		this(System.in, strictEoln);
	}
	public ValidatingScanner(InputStream source, boolean strictEoln) {
		this.in = source;
		this.strictEoln = strictEoln;
	}
	
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		}else{
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	
	public boolean eof() {
		return !hasNextByte();
	}
	
	private int getByte() {
		if (hasNextByte()) {
			return buffer[ptr];
		}else{
			return -1;
		}
	}
	
	private int readByte() {
		if (hasNextByte()) {
			return buffer[ptr++];
		}else{
			return -1;
		}
	}
	
	private void advance() {
		if (hasNextByte()) {
			ptr++;
		}
	}
	
	private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
	
	public long readLong() {
		if (eof()) {
			throw new NoSuchElementException();
		}
		long n = 0;
		boolean minus = false;
		int b = getByte();
		if (b == '-') {
			advance();
			minus = true;
			b = getByte();
		}
		if (b < '0' || '9' < b) {
			throw new InputMismatchException();
		}
		while(true){
			if ('0' <= b && b <= '9') {
				try {
					n = Math.multiplyExact(n, 10);
				} catch (ArithmeticException e) {
					throw new InputMismatchException();
				}
				n += b - '0';
			}else if(b == -1 || !isPrintableChar(b)){
				return minus ? -n : n;
			}else{
				throw new InputMismatchException();
			}
			advance();
			b = getByte();
		}
	}
	
	public int readInt() {
		long nl = readLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
			throw new InputMismatchException();
		}
		return (int) nl;
	}
	
	public int readInt(int min,int max) {
		if (min > max) throw new IllegalArgumentException();
		int n = readInt();
		if (n < min || n > max) throw new InputMismatchException();
		return n;
	}
	
	public void readSpace() {
		int b = readByte();
		if (b != ' ') throw new InputMismatchException();
	}
	
	public void readEoln() {
		if (strictEoln) {
			for(int i=0;i<EOLN.length();i++) {
				int b = readByte();
				if (b == -1 || b != EOLN.charAt(i)) {
					throw new InputMismatchException();
				}
			}
		}else{
			int b1 = getByte();
			if (b1 != '\r' && b1 != '\n') {
				throw new InputMismatchException();
			}
			advance();
			int b2 = getByte();
			if ((b1 == '\r' || b1 == '\n') && b1 != b2) {
				advance();
			}
		}

	}
	
	public void readEof() {
		if (!eof()) {
			throw new InputMismatchException();
		}
	}
	
	public void close() {try {in.close();} catch (IOException e) {}}
}