#include <bits/stdc++.h>
#define REP(i, s, n) for (int i = s; i < n; i++)
#define ALL(a) a.begin(), a.end()
#define MOD 1000000007
using namespace std;
typedef long long ll;

int main() {
    int N, P; cin >> N >> P;
    vector<int> A(N), B(N), C(N);
    REP(i, 0, N) cin >> A[i] >> B[i] >> C[i];

    vector<vector<int>> dp(N + 1, vector<int>(P + 1, 1 << 30));
    dp[0][0] = 0;
    REP(i, 0, N) {
        REP(j, 0, P + 1) {
            dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + A[i]);
            if (j + 1 <= P) dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j] + B[i]);
            if (j + 2 <= P) dp[i + 1][j + 2] = min(dp[i + 1][j + 2], dp[i][j] + C[i]);
            if (j + 3 <= P) dp[i + 1][j + 3] = min(dp[i + 1][j + 3], dp[i][j] + 1);
        }
    }

    // REP(i, 0, N + 1) {
    //     REP(j, 0, P + 1) {
    //         cout << setw(12) << setfill(' ') << dp[i][j];
    //     }
    //     cout << endl;
    // }

    cout << fixed << setprecision(15);
    cout << (double)dp[N][P] / N << endl;
    return 0;
}