#include<iostream>
#include<iomanip>
using namespace std;

typedef long long ll;

static ll dp[5001][15005];
const ll INF = 1ll<<60;

int main(){
    int n, p;
    cin >> n >> p;

    for(int i = 0; i <= n; i++){
        for(int j = 0; j <= n*3; j++){
            dp[i][j] = INF;
        }
    }

    dp[0][0] = 0;
    
    int a, b, c;

    for(int i = 0; i < n; i++){
        cin >> a >> b >> c;
        for(int j = 0; j <= 3*n; j++){
            if(dp[i][j] != INF){
                dp[i+1][j] = min(dp[i+1][j], dp[i][j] + a);
                dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j] + b);
                dp[i+1][j+2] = min(dp[i+1][j+2], dp[i][j] + c);
                dp[i+1][j+3] = min(dp[i+1][j+3], dp[i][j] + 1);
            }
        }
    }

    cout << fixed << setprecision(10) << (double)(dp[n][p]) / n << endl;
    return 0;
}