#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<ctime>
#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<memory>
#include<functional>
#include<set>
 
using namespace std;
 
#define ALL(g) (g).begin(),(g).end()
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define F(i,j,k) fill(i[0],i[0]+j*j,k)
#define P(p) cout<<(p)<<endl;
#define INF 1<<30
 
typedef long long ll;

int dy[8]={1,1,1,0,0,-1,-1,-1};
int dx[8]={-1,0,1,-1,1,-1,0,1};
struct S{
	int a,b,c;
};
bool asc(const S& left,const S& right){
	return left.c > right.c;
};
int n,p;
//int dp[5001][15001];
ll be[15001],af[15001];

int main(int argc, char const *argv[]) {
	cin >> n >> p;
	rep(i,3*n+1)be[i]=INF;
	be[p]=0;
	rep(i, n) {
		rep(j,3*n+1)af[j]=INF;
		int v[4];
		rep(k, 3) cin >> v[k];
		v[3] = 1;
		rep(j,p+1){
			rep(k,4){
				if(j>=k){
					af[j-k]=min(af[j-k],be[j]+v[k]);
				}
			}
		}
		swap(be,af);
	}
	printf("%.10lf\n", be[0]/(double)n);
	return 0;
}