#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <cstdlib>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional> 
#include <iomanip>
#include <unordered_map>
#include <memory.h>
#include <unordered_set>
#include <fstream>
#include <random>

using namespace std;

long long int dp[2][15001];
long long int p[5000][4];

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int N, P;

	cin >> N >> P;

	for (int i = 0; i < N; i++)
	{
		for (int j = 0; j < 3; j++)
		{
			cin >> p[i][j];
		}
		p[i][3] = 1;
	}

	for (int i = 0; i < 2; i++)
	{
		for (int j = 0; j <= P; j++)
		{
			dp[i][j] = 1e18;
		}
	}

	dp[1][0] = 0;

	for (int i = 0; i < N; i++)
	{
		for (int j = 0; j <= P; j++)
		{
			dp[0][j] = dp[1][j];
			dp[1][j] = 1e18;
		}
		for (int j = 0; j <= P; j++)
		{
			if (dp[0][j] >= 1e18) continue;
			for (int k = 0; k < 4; k++)
			{
				if (j + k <= P)
				{
					dp[1][j + k] = min(dp[1][j + k], dp[0][j] + p[i][k]);
				}
			}
		}
	}

	long double res = dp[1][P];
	res /= N;

	cout << fixed;
	cout.precision(6);

	cout << res << '\n';

	return 0;
}