#define _CRT_SECURE_NO_WARNINGS
#include<sstream>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<climits>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
#include<bitset>
#include<tuple>
#include<unordered_set>
#include<random>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())


int dp[2][15009];

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	int n, p;
	cin >> n >> p;
	int cur = 0;
	rep(i,n) {
		int a, b, c;
		cin >> a >> b >> c;
		rep(j, p + 1)dp[cur ^ 1][j] = INF;
		rep(j,p + 1) {
			dp[cur ^ 1][j] = min(dp[cur ^ 1][j], dp[cur][j] + a);
			dp[cur ^ 1][j + 1] = min(dp[cur ^ 1][j + 1], dp[cur][j] + b);
			dp[cur ^ 1][j + 2] = min(dp[cur ^ 1][j + 2], dp[cur][j] + c);
			dp[cur ^ 1][j + 3] = min(dp[cur ^ 1][j + 3], dp[cur][j] + 1);
		}

		cur ^= 1;
	}
	printf("%.5f\n", (double)dp[cur][p] / n);
	
	return 0;
}