#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int N, P;
ll v[5010][4];
ll dp[2][15010];

int main() {
  cin >> N >> P;
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < 3; j++) {
      cin >> v[i][j];
    }
    v[i][3] = 1;
  }

  int turn = 0;
  for (int i = 0; i <= P; i++) {
    dp[turn][i] = (i < 4 ? v[0][i] : 1LL << 60);
  }
  for (int i = 1; i < N; i++) {
    for (int j = 0; j <= P; j++) {
      dp[!turn][j] = 1LL << 60;
      for (int k = 0; k < 4 && j - k >= 0; k++) {
        dp[!turn][j] = min(dp[!turn][j], dp[turn][j - k] + v[i][k]);
      }
    }
    turn = !turn;
  }
  printf("%f\n", (double)dp[turn][P] / N);

  return 0;
}