// clang-format off
#include <cassert>
#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#include <iomanip>

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (b)-1; i >= (a); i--)
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep1(i,n) for(int i = 1; i <= (n); i++)
#define rrep(i, n) for(int i = (n)-1; i >= 0; i--)

#define pb push_back
#define mp make_pair
#define fst first
#define snd second
#define show(x) cout << #x << " = " << x << endl
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define pii pair<int, int>
#define vi vector<int>

using namespace std;
template<class S,class T> ostream& operator<<(ostream& o,const pair<S,T>& p){return o<<"("<<p.first<<","<<p.second<<")";}
template<class T> ostream& operator<<(ostream& o,const vector<T>& vc){o<<"sz = "<<vc.size()<<endl<<"[";for(const T& v:vc) o<<v<<",";o<<"]";return o;}
typedef long long ll;

int N;
int P;

int main()
{
    cin >> N >> P;
    vector<vector<ll>> a(N, vector<ll>(4));
    vector<vector<ll>> m(N, vector<ll>(3*N));
    const ll INF = 20000*N;
    
    rep(i, N){
        cin >> a[i][0] >> a[i][1] >> a[i][2];
        a[i][3] = 1;
    }
    rep(i, N){
        rep(j, P+1){
            m[i][j] = INF;
        }
    }

    rep(i, 4){
        if(i <= P){
            m[0][i]=a[0][i];            
        }
    }
    for(int i = 1; i < N; i++){
        rep(j, P+1){
            for(int s = 0; s <= 3 and j - s >= 0; s++){
                chmin(m[i][j], m[i-1][j-s]+a[i][s]);
            }
        }
    }
    cout << setprecision(9) << (long double)(m[N-1][P]) / N << endl;
    
    return 0;
}