/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.06.05 01:46:34
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

int main() {
    int n,p;cin >> n >> p;
    vector<double> dp(p+1,0);
    for (int i = 0; i < n; i++) {
        int a,b,c;cin >> a >> b >> c;
        for (int j = p; j >= 0; j--) {
            dp[j] = (dp[j] * i + a) / (i + 1);
            if (j - 1 >= 0) dp[j] = min(dp[j],(dp[j-1] * i + b) / (i + 1));
            if (j - 2 >= 0) dp[j] = min(dp[j],(dp[j-2] * i + c) / (i + 1));
            if (j - 3 >= 0) dp[j] = min(dp[j],(dp[j-3] * i + 1) / (i + 1));
        }
    }
    printf("%.10f",dp[p]);
    return 0;
}