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

signed main() {
  ios::sync_with_stdio(false);
  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<vector<int>> dp(2, vector<int>(p + 1, 0x3f3f3f3f));
  dp[0][0] = 0;
  for (int i = 0; i < n; ++i) {
    dp[~i & 1] = vector<int>(p + 1, 0x3f3f3f3f);
    for (int j = 0; j <= p; ++j) {
      dp[~i & 1][j] = min(dp[~i & 1][j], dp[i & 1][j] + a[i]);
      if (j + 1 <= p) {
        dp[~i & 1][j + 1] = min(dp[~i & 1][j + 1], dp[i & 1][j] + b[i]);
      }
      if (j + 2 <= p) {
        dp[~i & 1][j + 2] = min(dp[~i & 1][j + 2], dp[i & 1][j] + c[i]);
      }
      if (j + 3 <= p) {
        dp[~i & 1][j + 3] = min(dp[~i & 1][j + 3], dp[i & 1][j] + 1);
      }
    }
  }
  cout << fixed << setprecision(7) << (1.0 * dp[n & 1][p] / n) << endl;
  return 0;
}