#include<bits/stdc++.h>
using namespace std;
#pragma warning(disable:4996)
int main() {
	int N, P;
	scanf("%d", &N);
	scanf("%d", &P);
	vector < vector<int>>v(N, vector<int>(4));
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < 3; j++) {
			scanf("%d", &v[i][j]);
		}
		v[i][3] = 1;
	}
	int dp[4];
	memset(&dp, 0, sizeof(dp));
	
	for (int i = 0; i < N; i++) {
		for (int j = 3; j >= 0; j--) {
			if (j == 3) dp[j] = min({ dp[j] + v[i][0],dp[j - 1] + v[i][1],dp[j - 2] + v[i][2],dp[j - 3] + v[i][3] });
			else if(j==2)dp[j] = min({ dp[j] + v[i][0],dp[j - 1] + v[i][1],dp[j - 2] + v[i][2] });
			else if(j==1)dp[j] = min( dp[j] + v[i][0],dp[j - 1] + v[i][1] );
			else if (j == 0)dp[j] =  dp[j] + v[i][0];
		}
	}
	float ans = (float)(dp[P]) / N;
	printf("%.1f\n", ans);
	return 0;

}