#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pii = pair<int, int>;
template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define rep(i, n) rep2(i, 0, n)
#define rep2(i, m, n) for (int i = m; i < (n); i++)
#define per(i, b) per2(i, 0, b)
#define per2(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
#define ALL(c) (c).begin(), (c).end()
#define SZ(x) ((int)(x).size())

constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }

template <class T, class U>
void chmin(T& t, const U& u) {
    if (t > u) t = u;
}
template <class T, class U>
void chmax(T& t, const U& u) {
    if (t < u) t = u;
}

template <class T, class U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << "," << p.second << ")";
    return os;
}

template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "{";
    rep(i, v.size()) {
        if (i) os << ",";
        os << v[i];
    }
    os << "}";
    return os;
}

#ifdef LOCAL
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << H;
    debug_out(T...);
}
#define debug(...) \
    cerr << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif

template <unsigned int MOD>
struct ModInt {
    using uint = unsigned int;
    using ull = unsigned long long;
    using M = ModInt;

    uint v;

    ModInt(ll _v = 0) { set_norm(_v % MOD + MOD); }
    M& set_norm(uint _v) {  //[0, MOD * 2)->[0, MOD)
        v = (_v < MOD) ? _v : _v - MOD;
        return *this;
    }

    explicit operator bool() const { return v != 0; }
    M operator+(const M& a) const { return M().set_norm(v + a.v); }
    M operator-(const M& a) const { return M().set_norm(v + MOD - a.v); }
    M operator*(const M& a) const { return M().set_norm(ull(v) * a.v % MOD); }
    M operator/(const M& a) const { return *this * a.inv(); }
    M& operator+=(const M& a) { return *this = *this + a; }
    M& operator-=(const M& a) { return *this = *this - a; }
    M& operator*=(const M& a) { return *this = *this * a; }
    M& operator/=(const M& a) { return *this = *this / a; }
    M operator-() const { return M() - *this; }
    M& operator++(int) { return *this = *this + 1; }
    M& operator--(int) { return *this = *this - 1; }

    M pow(ll n) const {
        if (n < 0) return inv().pow(-n);
        M x = *this, res = 1;
        while (n) {
            if (n & 1) res *= x;
            x *= x;
            n >>= 1;
        }
        return res;
    }

    M inv() const {
        ll a = v, b = MOD, p = 1, q = 0, t;
        while (b != 0) {
            t = a / b;
            swap(a -= t * b, b);
            swap(p -= t * q, q);
        }
        return M(p);
    }

    bool operator==(const M& a) const { return v == a.v; }
    bool operator!=(const M& a) const { return v != a.v; }
    friend ostream& operator<<(ostream& os, const M& a) { return os << a.v; }
    static uint get_mod() { return MOD; }
};

using Mint = ModInt<1000000007>;

struct SCC {
    int n;
    VV<int> g, rg;
    V<int> vs, cmp;
    V<bool> vis;

    SCC() {}
    SCC(int n) : n(n) {
        g = rg = VV<int>(n);
        vs = cmp = V<int>(n);
        vis = V<bool>(n);
    }

    void add_edge(int from, int to) {
        g[from].push_back(to);
        rg[to].push_back(from);
    }

    void dfs(int v) {
        vis[v] = true;

        for (int to : g[v]) {
            if (!vis[to]) {
                dfs(to);
            }
        }

        vs.push_back(v);
    }

    void rdfs(int v, int k, V<int>& vec) {
        vis[v] = true;
        cmp[v] = k;
        vec.push_back(v);

        for (int to : rg[v]) {
            if (!vis[to]) {
                rdfs(to, k, vec);
            }
        }
    }

    VV<int> calc() {
        rep(v, n) if (!vis[v]) dfs(v);

        fill(vis.begin(), vis.end(), false);

        int k = 0;
        reverse(vs.begin(), vs.end());

        VV<int> vcomp;

        for (int v : vs) {
            if (!vis[v]) {
                V<int> vec;
                rdfs(v, k++, vec);
                vcomp.push_back(vec);
            }
        }

        return vcomp;
    }
};

int main() {
    int N;
    cin >> N;
    V<int> a(N);
    rep(i, N) cin >> a[i], --a[i];

    SCC scc(N);
    rep(i, N) scc.add_edge(i, a[i]);
    auto comps = scc.calc();

    V<int> rev(N, -1);

    rep(i, N) {
        if (scc.cmp[i] != scc.cmp[a[i]]) {
            if (rev[a[i]] != -1) {
                cout << 0 << endl;
                return 0;
            }
            rev[a[i]] = i;
        }
    }

    V<int> cnt(N + 1);
    Mint ans(1);

    for (auto& comp : comps) {  // cycles
        if (scc.cmp[comp[0]] != scc.cmp[a[comp[0]]]) continue;
        int sz = comp.size();
        V<int> len(sz);

        int pos = -1;

        rep(i, sz) {
            int v = rev[comp[i]];
            int k = 0;
            while (v != -1) {
                k++;
                v = rev[v];
            }
            len[i] = k;
            if (k > 0) {
                pos = i;
            }
        }

        if (pos == -1) {
            cnt[sz]++;
        } else {
            rotate(comp.begin(), comp.begin() + pos, comp.end());
            rotate(len.begin(), len.begin() + pos, len.end());
            int lst = 0;

            per(i, sz) {
                if (len[i]) {
                    int w = (lst - i + sz);
                    if (w > sz) w -= sz;
                    if (w > len[i]) {
                        ans *= 2;
                    } else if (w < len[i]) {
                        ans = 0;
                    }
                    lst = i;
                }
            }
        }

        debug(comp, len);
    }

    for (int l = 1; l <= N; ++l) {
        if (cnt[l] == 0) continue;
        if (l & 1) {
            V<Mint> dp_odd(cnt[l] + 1);
            dp_odd[0] = 1;
            for (int i = 1; i <= cnt[l]; ++i) {
                if (l > 1) {
                    dp_odd[i] = dp_odd[i - 1] * 2;
                } else {
                    dp_odd[i] = dp_odd[i - 1];
                }
                if (i >= 2) {
                    dp_odd[i] += dp_odd[i - 2] * (i - 1) * l;
                }
            }
            ans *= dp_odd[cnt[l]];
        } else {
            V<Mint> dp_even(cnt[l] + 1);
            dp_even[0] = 1;
            for (int i = 1; i <= cnt[l]; ++i) {
                dp_even[i] = dp_even[i - 1];
                if (i >= 2) {
                    dp_even[i] += dp_even[i - 2] * (i - 1) * l;
                }
            }
            ans *= dp_even[cnt[l]];
        }
    }

    cout << ans << endl;

    return 0;
}

Measured memory_bytes: 19440