#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000005
#define Inf64 1000000000000000001LL
int main(){
	
	int n,x,q;
	cin>>n>>x>>q;
	
	double ans = 0;
	
	rep(i,q){
		int m;
		cin>>m;
		set<int> s;
		rep(j,m){
			int t;
			cin>>t;
			s.insert(t);
		}
		if(s.count(x))ans += 2.0;
		else if(s.size()!=m)ans += 1.0;
	}
	ans /= 2.0;
	cout<<fixed<<setprecision(10)<<ans<<endl;
	
	return 0;
}