#include <iostream>
#include <vector>
#include <iomanip>

using ll = long long;

const int MAX_N = 5010;
ll INF = (1LL << 58);

ll dp[MAX_N * 3];

std::vector<ll> rank[MAX_N];

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

    for (int i = 0; i < n; i++) {
        ll a, b, c;
        std::cin >> a >> b >> c;
        rank[i].push_back(a);
        rank[i].push_back(b);
        rank[i].push_back(c);
        rank[i].push_back(1);
    }

    std::fill(dp, dp + MAX_N * 3, INF);
    dp[0] = 0;
    for (int i = 0; i < n; i++) {
        for (int j = (i + 1) * 3; j >= 0; j--) {
            ll value = INF;
            for (int k = 0; k <= 3; k++) {
                if (j - k < 0) break;
                value = std::min(value, dp[j - k] + rank[i][k]);
            }
            dp[j] = value;
        }
    }

    std::cout << std::fixed << std::setprecision(10) <<
        static_cast<double>(dp[p]) / static_cast<double>(n) << std::endl;

    return 0;
}