#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
const int N = 2000086, MOD = 998244353, INF = 0x3f3f3f3f;
int n, m, w[N];



int main() {
    int x, t, v, ans = 0;
    cin >> n >> x >> m;
    while (m--) {
        int s = 0;
        scanf("%d", &t);
        map<int, int> ma;
        while (t--) {
            scanf("%d", &v);
            if (v == x) s = 2;
            if (ma.count(v)) s = max(1, s);
            ma[v]++;
        }
        ans += s;
    }
    printf("%lf\n", ans / (double)2);
    return 0;
}