#include<bits/stdc++.h>
using namespace std;
int n,deg[100005],to[100005];
int cnt=0,Max,ans=1;
bool vis[100005];
void dfs(int u){
	vis[u]=true;
	cnt++;
	if(!vis[to[u]])dfs(to[u]);
}
void topo(){
	queue <int> q;
	for(int i=1;i<=n;i++)if(deg[i]==0)q.push(i);
	while(q.size()){
		int u=q.front();q.pop();
		vis[u]=true;
		if(--deg[to[u]]==0)q.push(to[u]);
	}
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>to[i];
		deg[to[i]]++;
	}
	topo();
	for(int u=1;u<=n;u++){
		if(vis[u])continue;
		cnt=0;
		dfs(u);
		if(cnt%2==0)ans*=2;
		else {
			cout<<0;
			return 0;
		}
	}
	cout<<ans;
	return 0;
}