#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <climits>
#include <map>
#include <queue>
#include <set>
#include <cstring>
#include <vector>

using namespace std;
typedef long long ll;

int main() {
  int N, P;
  cin >> N >> P;

  int A[N];
  int B[N];
  int C[N];

  for (int i = 0; i < N; ++i) {
    cin >> A[i] >> B[i] >> C[i];
  }

  vector<vector<int>> dp(N + 1, vector<int>(P + 1, INT_MAX));
  dp[0][0] = 0;

  for (int i = 1; i <= N; ++i) {
    int a = A[i - 1];
    int b = B[i - 1];
    int c = C[i - 1];

    for (int p = 0; p <= P; ++p) {
      if (dp[i - 1][p] != INT_MAX) {
        dp[i][p] = min(dp[i][p], dp[i - 1][p] + a);
        if (p + 1 <= P) {
          dp[i][p + 1] = min(dp[i][p + 1], dp[i - 1][p] + b);
        }
        if (p + 2 <= P) {
          dp[i][p + 2] = min(dp[i][p + 2], dp[i - 1][p] + c);
        }
        if (p + 3 <= P) {
          dp[i][p + 3] = min(dp[i][p + 3], dp[i - 1][p] + 1);
        }
      }
    }
  }

  cout << fixed << setprecision(10) << dp[N][P] * 1.0 / N << endl;

  return 0;
}