#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
using namespace std;

const int INF = INT_MAX / 2;

int main()
{
    int n, p;
    cin >> n >> p;

    vector<int> dp(p+1, INF);
    dp[p] = 0;
    for(int i=0; i<n; ++i){
        vector<int> v(4, 1);
        for(int i=0; i<3; ++i)
            cin >> v[i];

        vector<int> nextDp(p+1, INF);
        for(int j=0; j<=p; ++j){
            for(int k=0; k<=min(3,j); ++k){
                nextDp[j-k] = min(nextDp[j-k], dp[j] + v[k]);
            }
        }
        dp.swap(nextDp);
    }

    double ans = dp[0] / (double)n;
    printf("%.10f\n", ans);

    return 0;
}