#include <iostream>
#include <bitset>
#include <fstream>
#include <string>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <algorithm>
#include <numeric>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <deque>
#include <functional>
#include <cctype>
#include <list>
#include <limits>
//#include <boost/multiprecision/cpp_int.hpp>

const double EPS = (1e-10);


using namespace std;
using Int = long long;
//using namespace boost::multiprecision;

const Int MOD = 1000000007;

Int mod_pow(Int x, Int n) {
    Int res = 1;
    while(n > 0) {
        if(n & 1) res = (res * x) % MOD; //ビット演算(最下位ビットが1のとき)
        x = (x * x) % MOD;
        n >>= 1; //右シフト(n = n >> 1)
    }
    return res;
}

Int dp[2][15005];
Int p[5001][4];

int main(){
    cin.tie(0);

    int N, P; cin >> N >> P;
    for (int i = 0; i < N; i++){
        cin >> p[i][0] >> p[i][1] >> p[i][2];
        p[i][3] = 1;
    }

    //dp init
    for (int i = 0; i < 4; i++){
        dp[0][i] = p[0][i];
    }

    Int INF = 1e10;
    for (int i = 1; i < N; i++){
        for (int j = 0; j < (i+1)*3+1; j++){
            dp[i%2][j] = INF;
            for (int k = 0; k < 4; k++){
                if (j-k < 0) continue;
                if (j-k > (i)*3) continue; 
                dp[i%2][j] = min(dp[i%2][j], dp[(i-1)%2][j-k] + p[i][k]);
            }
        }
    }
    printf("%f\n", dp[(N-1)%2][P]/(double)N);

}