#include<iostream>
#include <iomanip>
#include<algorithm>
#define MAX_N 5010
#define MAX_P MAX_N*3
#define INF 1e15

long long dp[MAX_N][MAX_P];
int main(){
	std::cout<<std::fixed<<std::setprecision(6);
	
	int N, P, a, b, c;
	std::cin>>N>>P;
	
	for(int i = 0; i < MAX_N; i++)for(int j = 0; j < MAX_P; j++)dp[i][j]=INF;
	
	dp[0][0] = 0;
	
	for(int i = 0; i < N; i++){
		std::cin>>a>>b>>c;
		for(int j = 0; j <= N*3; j++){
			if(dp[i][j] == INF) continue;
			dp[i+1][j]   = std::min(dp[i][j]+a,dp[i+1][j]  );
			dp[i+1][j+1] = std::min(dp[i][j]+b,dp[i+1][j+1]);
			dp[i+1][j+2] = std::min(dp[i][j]+c,dp[i+1][j+2]);
			dp[i+1][j+3] = std::min(dp[i][j]+1,dp[i+1][j+3]);
		}
	}
	
	std::cout<<(double)dp[N][P]/N<<std::endl;
	
	return 0;
}