#include <bits/stdc++.h>

using namespace std;

int main() {
  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(P+1, INT_MAX);
  vector<int> nex(P+1, INT_MAX);
  cur[0] = 0;
  for(int i = 0; i < N; ++i) {
    fill(nex.begin(), nex.end(), INT_MAX);
    for(int j = P; j >= 0; --j) {
      if(j >= 0 && cur[j-0] != INT_MAX) nex[j] = min(nex[j], cur[j-0]+a[i]);
      if(j >= 1 && cur[j-1] != INT_MAX) nex[j] = min(nex[j], cur[j-1]+b[i]);
      if(j >= 2 && cur[j-2] != INT_MAX) nex[j] = min(nex[j], cur[j-2]+c[i]);
      if(j >= 3 && cur[j-3] != INT_MAX) nex[j] = min(nex[j], cur[j-3]+1);
    }
    cur.swap(nex);
  }
  cout << fixed << setprecision(12) << (double)cur[P]/N << endl;
  return 0;
}