#include <bits/stdc++.h>
using namespace std;

#define _p(...) (void)printf(__VA_ARGS__)
#define forr(x,arr) for(auto&& x:arr)
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) _rep3(i,0,n)
#define _rep3(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2,)(__VA_ARGS__)
#define _rrep2(i,n) _rrep3(i,0,n)
#define _rrep3(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2,)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define bit(n) (1LL<<(n))
#define sz(x) ((int)(x).size())
#define fst first
#define snd second
using ll=long long;using pii=pair<int,int>;
using vb=vector<bool>;using vs=vector<string>;
using vi=vector<int>;using vvi=vector<vi>;using vvvi=vector<vvi>;
using vl=vector<ll>;using vvl=vector<vl>;using vvvl=vector<vvl>;
using vd=vector<double>;using vvd=vector<vd>;using vvvd=vector<vvd>;
using vpii=vector<pii>;using vvpii=vector<vpii>;using vvvpii=vector<vvpii>;
template<typename T>T read(){T t;cin>>t;return t;}
template<class T,class U>ostream&operator<<(ostream&o,const pair<T,U>&p){o<<'('<<p.fst<<", "<<p.snd<<')';return o;}

template<class T> bool amin(T &a, const T &b) { if (b < a) { a = b; return 1; } return 0; }

void Main() {
  int n = read<int>();
  int p = read<int>();
  vvi R(4, vi(n, 1));

  rep(i, n) {
    R[0][i] = read<int>();
    R[1][i] = read<int>();
    R[2][i] = read<int>();
  }

  const int inf = 1e9+7;
  vvi dp(n+1, vi(p+1, inf));
  dp[0][0] = 0;

  rep(i, n) rep(j, p+1) {
    rep(k, 4) {
      if (j+k <= p) amin(dp[i+1][j+k], dp[i][j] + R[k][i]);
    }
  }

  double ans = dp[n][p];
  ans /= n;

  cout << fixed << setprecision(10) << ans << endl;
}
int main() { cin.tie(nullptr); ios::sync_with_stdio(false); Main(); return 0; }