#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (int)1e9 + 7;

int main() {
    int n, p; cin >> n >> p;
    vector<int> dp(p + 4, INF), dp2;
    dp[0] = 0;
    for (int _ = 0; _ < n; _++) {
        dp2.assign(p + 3, INF);
        vector<int> a(3);
        for (int j: {0, 1, 2}) cin >> a[j];
        a.emplace_back(1);
        for (int i = p; i >= 0; i--) {
            for (int j: {0, 1, 2, 3}) {
                chmin(dp2[i + j], dp[i] + a[j]);
            }
        }
        swap(dp, dp2);
    }
    cout << 1.0 * dp[p] / n << endl;
    return 0;
}