#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, X, Q;
    cin >> N >> X >> Q;

    double expected_value = 0.0;

    for (int i = 0; i < Q; ++i) {
        int M;
        cin >> M;
        vector<int> F(M);
        for (int j = 0; j < M; ++j) cin >> F[j];

        bool gull_acted = false;
        unordered_map<int, int> count;

        for (int f : F) {
            if (f == X) gull_acted = true;
            count[f]++;
        }

        if (gull_acted) expected_value += 1.0;
        else {
            bool multiple = false;
            for (auto &p : count) {
                if (p.second >= 2) { multiple = true; break; }
            }
            if (multiple) expected_value += 0.5;
        }
    }

    cout << fixed << setprecision(5) << expected_value << "\n";
    return 0;
}