#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <typename T>
bool chmax(T& a, const T& b)
{
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T>
bool chmin(T& a, const T& b)
{
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
constexpr ll inf = (1LL << 62);
int dp[5005][15005];
int main()
{
    ll n, p;
    cin >> n >> p;
    vector<int> a(n), b(n), c(n);
    for (ll i = 0; i < n; ++i) {
        cin >> a[i] >> b[i] >> c[i];
    }
    for (ll i = 0; i <= p; ++i) {
        for (ll j = 0; j <= n; ++j) {
            dp[j][i] = (1 << 30);
        }
    }
    dp[0][0] = 0;
    for (ll i = 0; i < n; ++i) {
        for (ll j = 0; j <= p; ++j) {
            if (j >= 3) {
                chmin(dp[i + 1][j], dp[i][j - 3] + 1);
            }
            if (j >= 2) {
                chmin(dp[i + 1][j], dp[i][j - 2] + c[i]);
            }
            if (j >= 1) {
                chmin(dp[i + 1][j], dp[i][j - 1] + b[i]);
            }
            chmin(dp[i + 1][j], dp[i][j] + a[i]);
        }
    }
    cout << fixed << setprecision(10) << static_cast<double>(dp[n][p]) / n << endl;
}