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

const long long int inf = 1e9;
//template<typename T> bool chmin(T& a,T b){if(a>b){a = b; return true;} return false;}
//template<typename T> bool chmax(T& a,T b){if(a<b){a = b; return true;} return false;}

int main(){
  long long int n,p; cin >> n >> p;
  vector<long long int> a(n),b(n),c(n);
  for(int i=0; n>i; ++i) cin >> a[i] >> b[i] >> c[i];
  //cost/val =  0/a[i],1/b[i],2/c[i],3/1
  //dp[n][p] := n問まで見てcostpとなった時の順位の総和の最小値
  long long int dp[2][p+1];
  for(int i=0; 2>i; ++i){
    for(int j=0; p>=j; ++j){
      dp[i][j] = inf;
    }
  }
  dp[0][0] = 0;
  for(int i=0; n>i; ++i){
    for(int j=0; p>=j; ++j){
      dp[1][j+0] = min(dp[1][j+0],dp[0][j]+a[i]);
      if(j+1<=p) dp[1][j+1] = min(dp[1][j+1],dp[0][j]+b[i]);
      if(j+2<=p) dp[1][j+2] = min(dp[1][j+2],dp[0][j]+c[i]);
      if(j+3<=p) dp[1][j+3] = min(dp[1][j+3],dp[0][j]+1LL);
    }
    for(int i=0; p>=i; ++i) dp[0][i]=dp[1][i];
    for(int i=0; p>=i; ++i) dp[1][i] = inf;
  }
  long double ans = static_cast<long double>(dp[0][p])/static_cast<long double>(n);
  cout << setprecision(15) << fixed << ans << endl;
}