#include<iostream>
#include <iomanip>
#include<algorithm>
#define MAX_P 15010
#define INF (long long)1e13


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