#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
//const int MOD = 1000000007;
const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const double pi = acos(-1.0);
const double EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

template<int mod>
struct Mod_Int{
    ll x;

    Mod_Int() : x(0) {}

    Mod_Int(ll y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

    Mod_Int &operator += (const Mod_Int &p){
        x = (x + p.x) % mod;
        return *this;
    }

    Mod_Int &operator -= (const Mod_Int &p){
        x = (x + mod - p.x) % mod;
        return *this;
    }

    Mod_Int &operator *= (const Mod_Int &p){
        x = (x * p.x) % mod;
        return *this;
    }

    Mod_Int &operator /= (const Mod_Int &p){
        *this *= p.inverse();
        return *this;
    }

    Mod_Int &operator ++ () {return *this += Mod_Int(1);}

    Mod_Int operator ++ (int){
        Mod_Int tmp = *this;
        ++*this;
        return tmp;
    }

    Mod_Int &operator -- () {return *this -= Mod_Int(1);}

    Mod_Int operator -- (int){
        Mod_Int tmp = *this;
        --*this;
        return tmp;
    }

    Mod_Int operator - () const {return Mod_Int(-x);}

    Mod_Int operator + (const Mod_Int &p) const {return Mod_Int(*this) += p;}

    Mod_Int operator - (const Mod_Int &p) const {return Mod_Int(*this) -= p;}

    Mod_Int operator * (const Mod_Int &p) const {return Mod_Int(*this) *= p;}

    Mod_Int operator / (const Mod_Int &p) const {return Mod_Int(*this) /= p;}

    bool operator == (const Mod_Int &p) const {return x == p.x;}

    bool operator != (const Mod_Int &p) const {return x != p.x;}

    Mod_Int inverse() const {
        assert(*this != Mod_Int(0));
        return pow(mod-2);
    }

    Mod_Int pow(ll k) const{
        Mod_Int now = *this, ret = 1;
        while(k){
            if(k&1) ret *= now;
            now *= now, k >>= 1;
        }
        return ret;
    }

    friend ostream &operator << (ostream &os, const Mod_Int &p){
        return os << p.x;
    }

    friend istream &operator >> (istream &is, Mod_Int &p){
        ll a;
        is >> a;
        p = Mod_Int<mod>(a);
        return is;
    }
};

template<typename T>
struct combination{
    vector<T> _fac, _ifac;

    combination(int n){
        _fac.resize(n+1), _ifac.resize(n+1);
        _fac[0] = 1;
        rep2(i, 1, n) _fac[i] = _fac[i-1]*i;
        _ifac[n] = _fac[n].inverse();
        rep3(i, n, 1) _ifac[i-1] = _ifac[i]*i;
    }

    T fac(int k) const {return _fac[k];}

    T ifac(int k) const {return _ifac[k];}

    T comb(int n, int k) const{
        if(k < 0 || n < k) return 0;
        return fac(n) * ifac(n-k) * ifac(k);
    }

    T perm(int n, int k) const{
        if(k < 0 || n < k) return 0;
        return fac(n) * ifac(n-k);
    }

    T second_stirling_number(ll n, int k){ //n個の区別できるボールをk個の区別できない箱に分割
        T ret = 0;
        rep(i, k+1){
            T tmp = comb(k, i)*T(k-i).pow(n);
            ret += ((i&1)? -tmp : tmp);
        }
        return ret*ifac(k);
    }
};

using mint = Mod_Int<MOD>;

template<int mod, int primitive_root>
struct Number_Theorem_Transform{
    using Mint = Mod_Int<mod>;

    const int y, x;
    vector<Mint> pw;

    Number_Theorem_Transform() : y(__builtin_ctz(mod-1)), x(mod>>y){
        pw.resize(y);
        pw[0] = Mint(primitive_root).pow(x);
        rep(i, y-1) pw[i+1] = pw[i]*pw[i];
    }

    void ntt(vector<Mint> &a, int n, bool inverse = false) const{
        assert((n&(n-1)) == 0);
        a.resize(n);
        rep(i, n){
            int j = 0;
            for(int k = 0; k < __builtin_ctz(n); k++){
                if(i&(1<<k)) j |= 1<<(__builtin_ctz(n)-1-k);
            }
            if(i < j) swap(a[i], a[j]);
        }
        for(int k = 1; k < n; k <<= 1){
            Mint w = 1, r = pw[y-1-__builtin_ctz(k)];
            if(inverse) r = r.inverse();
            rep(i, k){
                for(int j = 0; j < n; j += 2*k){
                    Mint s = a[j+i], t = a[j+k+i]*w;
                    a[j+i] = s+t, a[j+k+i] = s-t;
                }
                w *= r;
            }
        }
        if(inverse) rep(i, n) a[i] /= Mint(n);
    }

    vector<Mint> convolve(vector<Mint> a, vector<Mint> b) const{
        int n = 1<<(32-__builtin_clz(sz(a)+sz(b)-2));
        int k = sz(a)+sz(b)-1;
        vector<Mint> c(n);
        ntt(a, n), ntt(b, n);
        rep(i, n) c[i] = a[i]*b[i];
        ntt(c, n, true);
        c.resize(k);
        return c;
    }
};

int main(){
    int N;
    cin >> N;
    vector<int> cnt(100000, 0);
    rep(i, 2*N){
        int h; cin >> h; h--;
        cnt[h]++;
    }

    combination<mint> C(2*N);
    Number_Theorem_Transform<MOD, 3> NTT;

    mint dp[N+1];
    dp[0] = 1;
    rep2(i, 1, N) dp[i] = dp[i-1]*(2*i-1);

    priority_queue<pii, vector<pii>, greater<pii>> que;
    vector<mint> a[100000];
    rep(i, 100000){
        if(cnt[i] <= 1) continue;
        a[i].resize(1+cnt[i]/2);
        a[i][0] = 1;
        rep2(j, 1, cnt[i]/2){
            a[i][j] = a[i][j-1]*C.comb(cnt[i]-2*(j-1), 2)/mint(j);
        }
        que.emplace(sz(a[i]), i);
    }

    if(sz(que) == 0){
        cout << dp[N] << endl;
        return 0;
    }

    while(sz(que) >= 2){
        int i = que.top().second; que.pop();
        int j = que.top().second; que.pop();
        a[i] = NTT.convolve(a[i], a[j]);
        a[j].clear();
        que.emplace(sz(a[i]), i);
    }

    mint ans = 0;
    int i = que.top().second;
        
    rep(j, sz(a[i])){
        if(j&1) ans -= dp[N-j]*a[i][j];
        else ans += dp[N-j]*a[i][j];
    }
    
    cout << ans << endl;
}

Measured memory_bytes: 18168