#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
//-------------------------------------------------------

int N,P;
int A[50500][5];
int type[50500];

ll from[15050];
ll to[15050];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>P;
	FOR(i,3*N+1) from[i]=1<<30;
	from[P]=0;
	
	FOR(i,N) {
		FOR(j,3*N+1) to[j]=1<<30;
		cin>>A[i][0]>>A[i][1]>>A[i][2];
		A[i][3]=1;
		FOR(j,P+1) {
			if(j>=3) to[j-3]=min(to[j-3],from[j]+A[i][3]);
			if(j>=2) to[j-2]=min(to[j-2],from[j]+A[i][2]);
			if(j>=1) to[j-1]=min(to[j-1],from[j]+A[i][1]);
			if(j>=0) to[j-0]=min(to[j-0],from[j]+A[i][0]);
		}
		swap(from,to);
	}
	
	
	
	
	
	/*
	priority_queue<pair<double,int>> Q;
	FOR(i,N) {
		cin>>A[i][0]>>A[i][1]>>A[i][2];
		A[i][3]=1;
		Q.push({A[i][0]-A[i][1],i*10000+1});
		Q.push({(A[i][0]-A[i][2])/2.0,i*10000+2});
		Q.push({(A[i][0]-A[i][3])/3.0,i*10000+3});
	}
	
	while(P && Q.size()) {
		auto k=Q.top();
		Q.pop();
		x = k.second/10000;
		if(k.second%10 > P) continue;
		if(k.second/10%10 != type[x]) continue;
		P -= k.second%10;
		type[x] += k.second%10;
		
		for(y=type[x]+1;y<=3;y++) {
			Q.push({(A[x][type[x]]-A[x][y])*1.0/(y-type[x]),x*10000+type[x]*10+(y-type[x])});
		}
	}
	
	double ret=0;
	FOR(i,N) ret+=A[i][type[i]];
	*/
	_P("%.12lf\n",from[0]*1.0/N);
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n';
	FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	solve(); return 0;
}