/*
 * yuki472.cpp
 *
 *  Created on: 2017/03/12
 *      Author: Nishio
 */
#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=n;i<N;i++)
#define p(S) cout<<(S)<<endl
#define ck(a,b) (0<=(a)&&(a)<b)
using namespace std;

long long f[15010];
long long t[15010];
int main(){
	int N,P;
	cin>>N>>P;
	REP(i,0,3*N+1) f[i]=i<<30;
	int a[4];
	f[P]=0;
	REP(i,0,N){
		REP(j,0,3*N+1) t[j]=1<<30;
		cin>>a[0]>>a[1]>>a[2];
		a[3]=1;
		REP(j,0,P+1) REP(k,0,4)
			if(j>=k) t[j-k]=min(t[j-k],f[j]+a[k]);
		swap(t,f);
	}
	printf("%.6lf\n",1.*f[0]/N);
	return 0;
}