#include <iostream>
#include <utility>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <functional>
#include <iomanip>
#include <bitset>
#include <map>
#include <set>
#include <queue>
using namespace std;

int main(int argc, char const *argv[])
{
  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];
  }
  const int INF = 1e9;
  auto chmin = [](int &x, int y) -> int
  {
    if(y < x)x = y;
    return x;
  };
  vector<int> dp(P+1,INF);
  vector<int> ndp(P+1,INF);
  dp[0] = 0;
  for(int i=0;i<N;++i)
  {
    for(int j=P;j>=0;--j)
    {
      if(dp[j] != INF)
      {
        chmin(ndp[j],dp[j]+A[i]);
        if(j+1 <= P)chmin(ndp[j+1], dp[j]+B[i]);
        if(j+2 <= P)chmin(ndp[j+2], dp[j]+C[i]);
        if(j+3 <= P)chmin(ndp[j+3],dp[j]+1);
      }
    }
    dp = ndp;
    for(auto &x: ndp) x = INF;
  }
  
  std::cout << std::fixed << std::setprecision(15) << (double)dp[P]/N << std::endl;
}