#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define sar(a,n) {cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl;}

using namespace std;

template<typename S,typename T>auto&operator<<(ostream&o,pair<S,T>p){return o<<"{"<<p.fi<<","<<p.se<<"}";}
template<typename T>auto&operator<<(ostream&o,set<T>s){for(auto&e:s)o<<e<<" ";return o;}
template<typename S,typename T,typename U>
auto&operator<<(ostream&o,priority_queue<S,T,U>q){while(!q.empty())o<<q.top()<<" ",q.pop();return o;}
template<typename K,typename T>auto&operator<<(ostream&o,map<K,T>&m){for(auto&e:m)o<<e<<" ";return o;}
template<typename T>auto&operator<<(ostream&o,vector<T>v){for(auto&e:v)o<<e<<" ";return o;}
void ashow(){cout<<endl;}template<typename T,typename...A>void ashow(T t,A...a){cout<<t<<" ";ashow(a...);}
template<typename S,typename T,typename U>
struct TRI{S fi;T se;U th;TRI(){}TRI(S f,T s,U t):fi(f),se(s),th(t){}
bool operator<(const TRI&_)const{return(fi==_.fi)?((se==_.se)?(th<_.th):(se<_.se)):(fi<_.fi);}};
template<typename S,typename T,typename U>
auto&operator<<(ostream&o,TRI<S,T,U>&t){return o<<"{"<<t.fi<<","<<t.se<<","<<t.th<<"}";}

typedef pair<int, int> P;
typedef pair<ll, ll> pll;
typedef TRI<int, int, int> tri;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<P> vp;
typedef vector<double> vd;
typedef vector<string> vs;

const int MAX_N = 100005;

template <unsigned int mod>
class ModInt {
private:
    unsigned int v;
    static unsigned int norm(const unsigned int& x){ return x < mod ? x : x - mod; }
	static ModInt make(const unsigned int& x){ ModInt m; return m.v = x, m; }
    static ModInt inv(const ModInt& x){ return make(inverse(x.v, mod)); }
    static unsigned int inverse(int a, int m){
        int u[] = {a, 1, 0}, v[] = {m, 0, 1}, t;
        while(*v){
            t = *u / *v;
            swap(u[0] -= t * v[0], v[0]), swap(u[1] -= t * v[1], v[1]), swap(u[2] -= t * v[2], v[2]);
        }
        return (u[1] % m + m) % m;
    }

public:
    ModInt() : v{0}{}
    ModInt(const long long val) : v{norm(val % mod + mod)} {}
    ModInt(const ModInt<mod>& n) : v{n()} {}
	explicit operator bool() const noexcept { return v != 0; }
    bool operator!() const noexcept { return !static_cast<bool>(*this); }
    ModInt& operator=(const ModInt& n){ return v = n(), (*this); }
    ModInt& operator=(const long long val){ return v = norm(val % mod + mod), (*this); }
    ModInt operator+() const { return *this; }
    ModInt operator-() const { return v == 0 ? make(0) : make(mod - v); }
    ModInt operator+(const ModInt& val) const { return make(norm(v + val())); }
    ModInt operator-(const ModInt& val) const { return make(norm(v + mod - val())); }
    ModInt operator*(const ModInt& val) const { return make((long long)v * val() % mod); }
    ModInt operator/(const ModInt& val) const { return *this * inv(val); }
    ModInt& operator+=(const ModInt& val){ return *this = *this + val; }
    ModInt& operator-=(const ModInt& val){ return *this = *this - val; }
    ModInt& operator*=(const ModInt& val){ return *this = *this * val; }
    ModInt& operator/=(const ModInt& val){ return *this = *this / val; }
    ModInt operator+(const long long val) const { return ModInt{v + val}; }
    ModInt operator-(const long long val) const { return ModInt{v - val}; }
    ModInt operator*(const long long val) const { return ModInt{(long long)v * (val % mod)}; }
    ModInt operator/(const long long val) const { return ModInt{(long long)v * inv(val)}; }
    ModInt& operator+=(const long long val){ return *this = *this + val; }
    ModInt& operator-=(const long long val){ return *this = *this - val; }
    ModInt& operator*=(const long long val){ return *this = *this * val; }
    ModInt& operator/=(const long long val){ return *this = *this / val; }
    bool operator==(const ModInt& val) const { return v == val.v; }
    bool operator!=(const ModInt& val) const { return !(*this == val); }
    bool operator==(const long long val) const { return v == norm(val % mod + mod); }
    bool operator!=(const long long val) const { return !(*this == val); }
    unsigned int operator()() const { return v; }
    friend ModInt operator+(const long long val, const ModInt& n) { return n + val; }
    friend ModInt operator-(const long long val, const ModInt& n) { return ModInt{val - n()}; }
    friend ModInt operator*(const long long val, const ModInt& n) { return n * val; }
    friend ModInt operator/(const long long val, const ModInt& n) { return ModInt{val} / n; }
    friend bool operator==(const long long val, const ModInt& n) { return n == val; }
    friend bool operator!=(const long long val, const ModInt& n) { return !(val == n); }
    friend istream& operator>>(istream& is, ModInt& n){
        unsigned int v;
        return is >> v, n = v, is;
    }
    friend ostream& operator<<(ostream& os, const ModInt& n){ return (os << n()); }
    friend ModInt mod_pow(ModInt x, long long n){
        ModInt ans = 1;
        while(n){
            if(n & 1) ans *= x;
            x *= x, n >>= 1;
        }
        return ans;
    }
};

using mod = ModInt<MOD>;

mod inv[MAX_N],fac[MAX_N],finv[MAX_N];

void make()
{
	fac[0] = fac[1] = 1;
	finv[0] = finv[1] = 1;
	inv[1] = 1;
	for(int i=2;i<MAX_N;i++){
		inv[i] = MOD - inv[MOD % i] * (MOD / i);
		fac[i] = fac[i-1] * i;
		finv[i] = finv[i-1] * inv[i];
	}
}

mod comb(int a, int b)
{
	if(a<b) return 0;
	return fac[a] * finv[b] * finv[a-b];
}

vector<int> G[MAX_N], rG[MAX_N];
bool visit[MAX_N];
int cnt[MAX_N];

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    bool flag = true;
    rep(i,n){
        int a;
        cin >> a;
        --a;
        G[i].pb(a), rG[a].pb(i);
        if((int)rG[a].size() >= 3) flag = false;
    }
    if(!flag){
        cout << "0\n";
        return 0;
    }
    mod ans = 1;
    rep(i,n){
        if(!visit[i] && (int)rG[i].size() == 2){
            mod tm = 1;
            visit[i] = true;
            bool ar = true;
            int a = rG[i][0], b = rG[i][1];
            visit[a] = visit[b] = true;
            if(a == i || b == i){
                if(a != i) swap(a, b);
                if((int)rG[b].size() >= 1){
                    cout << "0\n";
                    return 0;
                }
                continue;
            }
            while(true){
                if((int)rG[a].size() + (int)rG[b].size() > 3){
                    cout << "0\n";
                    return 0;
                }else if((int)rG[a].size() + (int)rG[b].size() == 3){
                    if((int)rG[b].size() == 2 && !ar){
                        cout << "0\n";
                        return 0;
                    }
                    if((int)rG[a].size() < (int)rG[b].size()) swap(a, b);
                    if(rG[b][0] != a){
                        cout << "0\n";
                        return 0;
                    }
                    b = rG[a][0], a = rG[a][1];
                    visit[a] = visit[b] = true;
                    ar = true;
                    if(a == i || b == i){
                        if(a != i) swap(a, b);
                        if((int)rG[b].size() >= 1){
                            cout << "0\n";
                            return 0;
                        }
                        break;
                    }
                }else if((int)rG[a].size() == 2){
                    b = rG[a][0], a = rG[a][1];
                    visit[a] = visit[b] = true;
                    ar = true;
                    if(a == i || b == i){
                        if(a != i) swap(a, b);
                        if((int)rG[b].size() >= 1){
                            cout << "0\n";
                            return 0;
                        }
                        break;
                    }
                }else if((int)rG[a].size() == 1){
                    if((int)rG[b].size() == 1){
                        if(rG[b][0] == a){
                            b = a, a = rG[a][0];
                            visit[a] = true;
                            ar = false;
                            if(a == i) break;
                        }else{
                            int tmp = a;
                            a = rG[b][0], b = rG[tmp][0];
                            visit[a] = visit[b] = true;
                            if(a == i || b == i){
                                if(b == i && !ar){
                                    cout << "0\n";
                                    return 0;
                                }
                                if(a != i) swap(a, b);
                                if((int)rG[b].size() >= 1){
                                    cout << "0\n";
                                    return 0;
                                }
                                break;
                            }
                        }
                    }else{
                        b = a, a = rG[a][0];
                        visit[a] = true;
                        if(ar) tm *= 2;
                        ar = false;
                        if(a == i) break;
                    }
                }else{
                    if(rG[b].size() == 2){
                        if(ar){
                            a = rG[b][0], b = rG[b][1];
                            visit[a] = visit[b] = true;
                            ar = true;
                            if(a == i || b == i){
                                if(a != i) swap(a, b);
                                if((int)rG[b].size() >= 1){
                                    cout << "0\n";
                                    return 0;
                                }
                                break;
                            }
                        }else{
                            cout << "0\n";
                            return 0;
                        }
                    }else if(rG[b].size() == 1){
                        if(rG[b][0] == a){
                            cout << "0\n";
                            return 0;
                        }
                        int tmp = a;
                        a = rG[b][0], b = tmp;
                        visit[a] = true;
                        if(ar) tm *= 2;
                        ar = false;
                        if(a == i) break;
                    }else{
                        cout << "0\n";
                        return 0;
                    }
                }
            }
            ans *= tm;
        }
    }
    make();
    rep(i,n){
        if(!visit[i]){
            int ln = 0, cur = i;
            do{
                ++ln, visit[cur] = true;
                cur = G[cur][0];
            }while(!visit[cur]);
            ++cnt[ln];
        }
    }
    srep(i,1,n+1){
        if(cnt[i] == 0) continue;
        mod tm = 1, res = 0;
        rep(j,cnt[i]/2+1){
            if(i > 1 && i % 2) res += comb(cnt[i], 2 * j) * tm * mod_pow((mod)i, j) * mod_pow((mod)2, cnt[i] - 2*j);
            else res += comb(cnt[i], 2 * j) * tm * mod_pow((mod)i, j);
            tm *= (2 * j + 1);
        }
        ans *= res;
    }
    cout << ans << "\n";
    return 0;
}

Measured memory_bytes: 12544