#ifndef LOCAL
#include <bits/stdc++.h>

using namespace std;

#define debug(...) (void(0))
#else
#include "algo/debug.h"
#endif

void solve() {
    int N, P; cin >> N >> P;
    vector<int> A(N), B(N), C(N);
    for(int i = 0; i < N; i++) cin >> A[i] >> B[i] >> C[i];
    vector<int64_t> dp(P + 1, 1e18);
    dp[0] = 0;
    for(int i = 0; i < N; i++) {
        vector<int64_t> ndp(P + 1, 1e18);
        for(int j = 0; j <= P; j++) {
            ndp[j] = min(ndp[j], dp[j] + A[i]);
            if(j + 1 <= P) ndp[j + 1] = min(ndp[j + 1], dp[j] + B[i]);
            if(j + 2 <= P) ndp[j + 2] = min(ndp[j + 2], dp[j] + C[i]);
            if(j + 3 <= P) ndp[j + 3] = min(ndp[j + 3], dp[j] + 1);
        }
        dp.swap(ndp);
    }
    cout << fixed << setprecision(16) << dp.back() / double(N) << "\n";
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int tt = 1;
    // std::cin >> tt;
    while (tt--) {
        solve();
    }
}