// #includes {{{
#include <algorithm>
#include <numeric>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <list>
#include <deque>
#include <stack>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cassert>
#include <cstring>
#include <cmath>
using namespace std;
// }}}
// pre-written code {{{
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define RREP(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define FOR(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();++i)
#define LET(x,a) __typeof(a) x(a)
//#define IFOR(i,it,c) for(__typeof((c).begin())it=(c).begin();it!=(c).end();++it,++i)
#define ALL(c) (c).begin(), (c).end()
#define MP make_pair

#define EXIST(e,s) ((s).find(e)!=(s).end())

#define RESET(a) memset((a),0,sizeof(a))
#define SET(a) memset((a),-1,sizeof(a))
#define PB push_back
#define DEC(it,command) __typeof(command) it=command

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#define debug2(x) cerr << #x << " = [";REP(__ind,(x).size()){cerr << (x)[__ind] << ", ";}cerr << "] (L" << __LINE__ << ")" << endl;

const int INF=0x3f3f3f3f;

typedef long long Int;
typedef unsigned long long uInt;
#ifdef __MINGW32__
typedef double rn;
#else
typedef double rn;
#endif

typedef pair<int,int> pii;

/*
#ifdef MYDEBUG
#include"debug.h"
#include"print.h"
#endif
*/
// }}}

int N,P;

int t[5050][4];

rn dp[2][15050];
const rn inf = 1.0L/0.0L;

int main(){
	cin>>N>>P;
	REP(i,N)cin>>t[i][0]>>t[i][1]>>t[i][2],t[i][3]=1;
	for(int p=0;p<=P;p++){
		dp[0][p] = (p==0)?0.0L:inf;
	}
	REP(i,N){
		int from = i%2, to = (i+1)%2;
		for(int p=0;p<=P;p++)dp[to][p] = inf;
		for(int p=0;p<=P;p++){
			for(int j=0;j<=3;j++){
				if(p-j<0)continue;
				dp[to][p] = min(dp[to][p],dp[from][p-j]+t[i][j]);
			}
		}
	}
	printf("%.10lf\n",dp[N%2][P]/N);
	return 0;
}