#include <bits/stdc++.h>

using namespace std;

const int maxn = ,mod = 1e9+;

int du[maxn],to[maxn],vis[maxn];

int n,cnt;

long long ans,qpow[maxn];

int main()

{

    freopen("road.in","r",stdin);

    freopen("road.out","w",stdout);

    queue <int> q;

    scanf("%d",&n);

    qpow[] = ;

    for (int i = ; i <= n; i++)

        qpow[i] = (qpow[i - ] * ) % mod;

    for (int i = ; i <= n; i++)

    {

        scanf("%d",&to[i]);

        du[to[i]]++;

    }

    for (int i = ; i <= n; i++)

        if (!du[i])

    {

        q.push(i);

        cnt++;

    }

    while (!q.empty())

    {

        int u = q.front();

        vis[u] = ;

        q.pop();

        du[to[u]]--;

        if (du[to[u]] == )

        {

            cnt++;

            q.push(to[u]);

        }

    }

    ans = qpow[cnt];

    for(int i = ; i <= n; i++)

        if (!vis[i])

    {

        cnt = ;

        int x = i;

        while (!vis[x])

        {

            cnt++;

            vis[x] = ;

            x = to[x];

        }

        ans = (ans * (qpow[cnt] -  + mod)) % mod;

    }

    printf("%lld\n",ans);

    return ;

}