#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define pb push_back
int dy[]={0, 0, 1, -1, 1, 1, -1, -1};
int dx[]={1, -1, 0, 0, 1, -1, -1, 1};

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define mp make_pair
#define fi first
#define sc second
#define INF (1e9)

int N,P;
int a[4][5000];
bool done[5001][15001];
int memo[5001][15001];

int solve(int i,int j) {
	if(done[i][j]) {
		return memo[i][j];
	}
	if(i == N - 1) {
		double ret;
		if(j < 4) {
			ret = a[j][i];
		}
		else 
			ret = INF;
		done[i][j] = true;
		return memo[i][j] = ret;
	}

	double x = INF,y = INF,z = INF,w = INF;

	x = (solve(i + 1,j) + a[0][i]);

	if(j > 0) {
		y = (solve(i + 1,j - 1) + a[1][i]);
	} 
	if(j > 1) {
		z = (solve(i + 1,j - 2) + a[2][i]);
	}
	if(j > 2) {
		w = (solve(i + 1,j - 3) + a[3][i]);
	}
	done[i][j] = true;
	return memo[i][j] = min(min(x,y),min(z,w));
}


int main(){
	scanf("%d%d",&N,&P);
	REP(i,N) {
		scanf("%d%d%d",a[0]+i,a[1]+i,a[2]+i);
		a[3][i] = 1;
	}

	
	printf("%0.10f\n",solve(0,P) / (double)N);
	return 0;
}