#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <bitset>
#include <map>
#include <unordered_map>
#include <list>
#include <numeric>
#include <utility>
#include <iterator>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <ctime>
#include <cassert>

#define INF 1000000000
#define LINF 9000000000000000000
#define mod 1000000007

#define rep(i,n) for(int i=0;i<int(n);i++)
#define rrep(i,n) for(int i=n-1;i>=0;i--)
#define REP(i,a,b) for(int i=(a);i<int(b);i++)
#define all(x) (x).begin(),x.end()
#define pb push_back
#define mp make_pair

using namespace std;

/*
cin.tie(0);
ios::sync_with_stdio(false);
*/

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef pair<int,int> pi;

int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
int ddx[8]={-1,-1,0,1,1,1,0,-1};
int ddy[8]={0,1,1,1,0,-1,-1,-1};
bool debug=false;

/*---------------------------------------------------*/

int n,p;
int a[5005][4];
int dp[2][15005];

int main(){
  cin>>n>>p;
  rep(i,n){
    cin>>a[i][0]>>a[i][1]>>a[i][2];
    a[i][3]=1;
  }
  rep(i,2)rep(j,15005)dp[i][j]=INF;
  dp[0][0]=0;
  rep(i,n){
    rep(j,p+1){
      rep(k,4){
	if(j+k<=p)dp[1][j+k]=min(dp[0][j]+a[i][k],dp[1][j+k]);
      }
    }
    rep(j,p+1){
      dp[0][j]=dp[1][j];
      dp[1][j]=INF;
    }
  }
  //rep(i,p+1)cout<<"debug: "<<dp[0][i]<<endl;
  printf("%.9f\n",(double)dp[0][p]/n);
  return 0;
}