#include <bits/stdc++.h>

using namespace std;

const int INF = 1<<30;

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

  int n, p;
  cin >> n >> p;
  vector<int> a(n), b(n), c(n);
  for (int i = 0; i < n; i++)
    cin >> a[i] >> b[i] >> c[i];

  vector<int> cur = vector<int>(p + 10);
  vector<int> nxt = cur;
  for (int i = 0; i < n; i++) {
    fill(nxt.begin(), nxt.end(), INF);
    for (int j = 0; j <= p; j++) {
      nxt[j] = min(nxt[j], cur[j] + a[i]);
      nxt[j+1] = min(nxt[j+1], cur[j] + b[i]);
      nxt[j+2] = min(nxt[j+2], cur[j] + c[i]);
      nxt[j+3] = min(nxt[j+3], cur[j] + 1);
    }
    cur = nxt;
  }

  double ret = cur[p];
  cout << fixed << setprecision(9) << ret/n << endl;
  
  return 0;
}