#include <bits/stdc++.h>
using namespace std;

#define INF 1.1e9
#define LINF 1.1e18
#define FOR(i,a,b) for (int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define BIT(x,n) bitset<n>(x)
#define PI 3.14159265358979323846

typedef long long ll;
typedef pair<int,int> P;
typedef pair<ll,P> PP;

//-----------------------------------------------------------------------------

int dp[2][15010];
int n,p;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	REP(i,2) REP(j,15010) dp[i][j]=INF;

	cin>>n>>p;
	dp[0][0]=0;
	FOR(i,0,n) {
		int a[4];
		REP(j,3) cin>>a[j];
		a[3]=1;
		REP(j,min(p,3*i)+1) {
			if(dp[i&1][j]!=INF) {
				REP(k,4) dp[(i+1)&1][j+k]=min(dp[(i+1)&1][j+k],dp[i&1][j]+a[k]);
			}
		}
	}
	double ans=(double)dp[n&1][p]/n;
	printf("%.10f\n",ans);

	return 0;
}