#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1e16;

int main()
{
	int N, P;
	cin >> N >> P;
	vector<vector<ll>> dp(N + 1, vector<ll>(P + 1, INF));
	dp[0][0] = 0;
	for (int i = 0, a[4]; i < N; i++) {
		cin >> a[0] >> a[1] >> a[2]; a[3] = 1;
		for (int j = 0; j <= 3; j++) {
			for (int k = 0; k <= P - j; k++) {
				if (dp[i][k] != INF) {
					dp[i + 1][k + j] = min(dp[i + 1][k + j], dp[i][k] + a[j]);
				}
			}
		}
	}
	cout << fixed << setprecision(8) << ((double)dp[N][P] / N) << endl;
	return 0;
}