#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <cassert>
#include "testlib.h"
using ll = long long;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); i++)

const ll MOD = 1000000007;
ll modpow(ll a, ll n, ll mod) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}

ll modinv(ll i, ll mod) {
    return modpow(i, mod - 2, mod);
}

ll fact(ll n, ll mod) {
    ll ans = 1;
    rep(i, n) {
        ans = ans * (i + 1) % mod;
    }
    return ans;
}

ll comb(ll n, ll a, ll mod) {
    ll ans = 1, denom = 1;
    rep(i, a) {
        ans = ans * (n - i) % mod;
        denom = denom * (i + 1) % mod;
    }
    ans = ans * modinv(denom, mod) % mod;
    return ans;
}

int main(int argc, char* argv[]) {
    registerValidation(argc, argv);
    int n = inf.readInt(1, 100000, "n");
    inf.readEoln();
    vector<int> p(n);
    vector<int> counter(n, 0);
    for (size_t i = 0; i < n; i++)
    {
        p[i] = inf.readInt(1, n, "p_i");
        if (i != n - 1)
        {
            inf.readSpace();
        }
        p[i]--;
        counter[p[i]]++;
    }
    inf.readEoln();
    inf.readEof();
    for (size_t i = 0; i < n; i++)
    {
        assert(counter[i] == 1);
    }
    map<int, int> mp;
    vector<bool> visited(n, false);
    for (size_t i = 0; i < n; i++)
    {
        if (!visited[i])
        {
            int l = 0;
            int v = i;
            while (!visited[v])
            {
                visited[v] = true;
                v = p[v];
                l++;
            }
            mp[l]++;
        }
    }
    bool half = true;
    ll ans = fact(n, MOD);
    for (auto itr = mp.begin(); itr != mp.end(); ++itr) {
        int k = itr->first;
        int v = itr->second;
        if (k % 2 == 0 || v >= 2)
        {
            half = false;
        }
        ans *= modinv(modpow(k, v, MOD), MOD);
        ans %= MOD;
        ans *= modinv(fact(v, MOD), MOD);
        ans %= MOD;
    }
    if (half && n != 1)
    {
        ans *= modinv(2, MOD);
        ans %= MOD;
    }
    cout << ans << "\n";
}