#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
constexpr ll mod = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int>P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-12;
const ld pi = acos(-1.0);

void chmin(int &a, int b) {
	a = min(a, b);
}
void chmax(int &a, int b) {
	a = max(a, b);
}
ll mod_pow(ll a, ll n, ll m = mod) {
	a %= m;
	ll res = 1;
	while (n) {
		if (n & 1)res = res * a%m;
		a = a * a%m; n >>= 1;
	}
	return res;
}

struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n%mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint &a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint &a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint &a, modint b) { a.n = ((ll)a.n*b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
	if (n == 0)return modint(1);
	modint res = (a*a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p%a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }
const int max_n = 1 << 18;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}

int dx[4] = { 0,1,0,-1 };
int dy[4] = { 1,0,-1,0 };




void solve() {
	int n; cin >> n;
	vector<int> a(n);
	rep(i, n) {
		cin >> a[i]; a[i]--;
	}
	vector<int> in(n);
	rep(i, n)in[a[i]]++;
	rep(i, n) {
		if (in[i] >= 3) {
			cout << 0 << "\n"; return;
		}
	}

	vector<vector<int>> rG(n);
	rep(i, n) {
		rG[a[i]].push_back(i);
	}

	vector<vector<int>> loops;
	vector<bool> used(n, false);
	rep(i, n) {
		if (used[i])continue;
		int cur = i;
		map<int, bool> mp;
		mp[cur] = true; cur = a[cur];
		vector<int> ids; ids.push_back(i);
		int chk = -1;
		while (true) {
			if (used[cur]) {
				break;
			}
			if (mp[cur]) {
				chk = cur; break;
			}
			ids.push_back(cur);
			mp[cur] = true;
			cur = a[cur];
		}

		for (int id : ids)used[id] = true;
		if (chk < 0)continue;
		vector<int> cloop;
		cloop.push_back(chk);
		while (ids.back() != chk) {
			cloop.push_back(ids.back());
			ids.pop_back();
		}
		reverse(all(cloop));
		loops.push_back(cloop);
	}

	vector<bool> inloop(n, false);
	for (vector<int> &cloop : loops) {
		for (int id : cloop)inloop[id] = true;
	}

	modint ans = 1;
	vector<int> nums(n + 1);
	for (vector<int> &cloop : loops) {

		vector<int> num(cloop.size(), 0);
		bool exi = false;
		rep(j, cloop.size()) {
			int id = cloop[j];
			if (rG[id].size() == 2) {
				exi = true;
				int tmp = 1;

				int cur = rG[id][0];
				if (inloop[cur])cur = rG[id][1];
				while (rG[cur].size() >= 1) {
					if (rG[cur].size() == 2) {
						cout << 0 << "\n"; return;
					}
					tmp++;
					cur = rG[cur][0];
				}
				num[j] = tmp;
			}

		}
		if (!exi)nums[cloop.size()]++;

		modint cans = 1;
		vector<int> locs;
		rep(j, cloop.size())if(num[j]>0)locs.push_back(j);
		rep(j, cloop.size())if(num[j]>0)locs.push_back(j+cloop.size());
		rep(j, cloop.size()) {
			if (num[j] == 0)continue;
			int id = lower_bound(all(locs), j + cloop.size()) - locs.begin();
			id--;
			id = locs[id];
			int prenum = j + cloop.size() - id - 1;
			if (num[j] > prenum + 1) {
				cans *= 0;
				//cout << "e?" << "\n";
			}
			else if (num[j] <= prenum) {
				cans *= 2;
			}
		}

		ans *= cans;
	}
	vector<modint> facts(n + 1);
	facts[0] = 1;
	facts[2] = 1;
	for (int i = 4; i <= n; i += 2) {
		facts[i] = facts[i - 2] * (modint)(i - 1);
	}
	rep1(i, n) {
		if (nums[i] == 0)continue;
		int cnt = nums[i];
		modint csum = 0;
		for (int ps = 0; ps <= cnt; ps += 2) {
			modint c = comb(cnt, ps);
			c*=facts[ps];
			if (i > 1 && i % 2) {
				c *= (modint)2 ^ (cnt - ps);
			}
			c *= (modint)i ^ (ps / 2);
			csum += c;
		}
		ans *= csum;
	}
	cout << ans << "\n";
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout << fixed << setprecision(10);
	init_f();
	//init();
	solve();
	stop
		return 0;
}


Measured memory_bytes: 17840