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

template<typename T>
struct Z_p{
	using Type = typename decay<decltype(T::value)>::type;
	static vector<Type> mod_inv; 
	constexpr Z_p(): value(){ }
	template<typename U> Z_p(const U &x){ value = normalize(x); }
	template<typename U> static Type normalize(const U &x){
		Type v;
		if(-mod() <= x && x < mod()) v = static_cast<Type>(x);
		else v = static_cast<Type>(x % mod());
		if(v < 0) v += mod();
		return v;
	}
	const Type& operator()() const{ return value; }
	template<typename U> explicit operator U() const{ return static_cast<U>(value); }
	constexpr static Type mod(){ return T::value; }
	Z_p &operator+=(const Z_p &otr){ if((value += otr.value) >= mod()) value -= mod(); return *this; }
	Z_p &operator-=(const Z_p &otr){ if((value -= otr.value) < 0) value += mod(); return *this; }
	template<typename U> Z_p &operator+=(const U &otr){ return *this += Z_p(otr); }
	template<typename U> Z_p &operator-=(const U &otr){ return *this -= Z_p(otr); }
	Z_p &operator++(){ return *this += 1; }
	Z_p &operator--(){ return *this -= 1; }
	Z_p operator++(int){ Z_p result(*this); *this += 1; return result; }
	Z_p operator--(int){ Z_p result(*this); *this -= 1; return result; }
	Z_p operator-() const{ return Z_p(-value); }
	template<typename U = T>
	typename enable_if<is_same<typename Z_p<U>::Type, int>::value, Z_p>::type &operator*=(const Z_p& rhs){
		#ifdef _WIN32
		uint64_t x = static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value);
		uint32_t xh = static_cast<uint32_t>(x >> 32), xl = static_cast<uint32_t>(x), d, m;
		asm(
			"divl %4; \n\t"
			: "=a" (d), "=d" (m)
			: "d" (xh), "a" (xl), "r" (mod())
		);
		value = m;
		#else
		value = normalize(static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value));
		#endif
		return *this;
	}
	template<typename U = T>
	typename enable_if<is_same<typename Z_p<U>::Type, int64_t>::value, Z_p>::type &operator*=(const Z_p &rhs){
		int64_t q = static_cast<int64_t>(static_cast<long double>(value) * rhs.value / mod());
		value = normalize(value * rhs.value - q * mod());
		return *this;
	}
	template<typename U = T>
	typename enable_if<!is_integral<typename Z_p<U>::Type>::value, Z_p>::type &operator*=(const Z_p &rhs){
		value = normalize(value * rhs.value);
		return *this;
	}
	Z_p operator^(long long e) const{
		Z_p b = *this, res = 1;
		if(e < 0) b = 1 / b, e = -e;
		for(; e; b *= b, e >>= 1) if(e & 1) res *= b;
		return res;
	}
	Z_p &operator^=(const long long &e){ return *this = *this ^ e; }
	Z_p &operator/=(const Z_p &otr){
		Type a = otr.value, m = mod(), u = 0, v = 1;
		if(a < int(mod_inv.size())) return *this *= mod_inv[a];
		while(a){
			Type t = m / a;
			m -= t * a; swap(a, m);
			u -= t * v; swap(u, v);
		}
		assert(m == 1);
		return *this *= u;
	}
	template<typename U> friend const Z_p<U> &abs(const Z_p<U> &v){ return v; }
	template<typename U> friend bool operator==(const Z_p<U> &lhs, const Z_p<U> &rhs);
	template<typename U> friend bool operator<(const Z_p<U> &lhs, const Z_p<U> &rhs);
	template<typename U> friend istream &operator>>(istream &in, Z_p<U> &number);
	Type value;
};
template<typename T> bool operator==(const Z_p<T> &lhs, const Z_p<T> &rhs){ return lhs.value == rhs.value; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> bool operator==(const Z_p<T>& lhs, U rhs){ return lhs == Z_p<T>(rhs); }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> bool operator==(U lhs, const Z_p<T> &rhs){ return Z_p<T>(lhs) == rhs; }
template<typename T> bool operator!=(const Z_p<T> &lhs, const Z_p<T> &rhs){ return !(lhs == rhs); }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> bool operator!=(const Z_p<T> &lhs, U rhs){ return !(lhs == rhs); }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> bool operator!=(U lhs, const Z_p<T> &rhs){ return !(lhs == rhs); }
template<typename T> bool operator<(const Z_p<T> &lhs, const Z_p<T> &rhs){ return lhs.value < rhs.value; }
template<typename T> Z_p<T> operator+(const Z_p<T> &lhs, const Z_p<T> &rhs){ return Z_p<T>(lhs) += rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator+(const Z_p<T> &lhs, U rhs){ return Z_p<T>(lhs) += rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator+(U lhs, const Z_p<T> &rhs){ return Z_p<T>(lhs) += rhs; }
template<typename T> Z_p<T> operator-(const Z_p<T> &lhs, const Z_p<T> &rhs){ return Z_p<T>(lhs) -= rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator-(const Z_p<T>& lhs, U rhs){ return Z_p<T>(lhs) -= rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator-(U lhs, const Z_p<T> &rhs){ return Z_p<T>(lhs) -= rhs; }
template<typename T> Z_p<T> operator*(const Z_p<T> &lhs, const Z_p<T> &rhs){ return Z_p<T>(lhs) *= rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator*(const Z_p<T>& lhs, U rhs){ return Z_p<T>(lhs) *= rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator*(U lhs, const Z_p<T> &rhs){ return Z_p<T>(lhs) *= rhs; }
template<typename T> Z_p<T> operator/(const Z_p<T> &lhs, const Z_p<T> &rhs) { return Z_p<T>(lhs) /= rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator/(const Z_p<T>& lhs, U rhs) { return Z_p<T>(lhs) /= rhs; }
template<typename T, typename U, typename enable_if<is_integral<U>::value>::type* = nullptr> Z_p<T> operator/(U lhs, const Z_p<T> &rhs) { return Z_p<T>(lhs) /= rhs; }
template<typename T> istream &operator>>(istream &in, Z_p<T> &number){
	typename common_type<typename Z_p<T>::Type, int64_t>::type x;
	in >> x;
	number.value = Z_p<T>::normalize(x);
	return in;
}
template<typename T> ostream &operator<<(ostream &out, const Z_p<T> &number){ return out << number(); }

/*
using ModType = int;
struct VarMod{ static ModType value; };
ModType VarMod::value;
ModType &mod = VarMod::value;
using Zp = Z_p<VarMod>;
*/

constexpr int mod = 1e9 + 7;
//constexpr int mod = (119 << 23) + 1;
using Zp = Z_p<integral_constant<decay<decltype(mod)>::type, mod>>;

template<typename T> vector<typename Z_p<T>::Type> Z_p<T>::mod_inv;
template<typename T = integral_constant<decay<decltype(mod)>::type, mod>>
void precalc_inverse(size_t SZ){
	auto &inv = Z_p<T>::mod_inv;
	if(inv.empty()) inv.assign(2, 1);
	for(; inv.size() <= SZ; ) inv.push_back((mod - 1LL * mod / int(inv.size()) * inv[mod % int(inv.size())] % mod) % mod);
}

// Requires Z_p
template<int SZ, typename T = Zp>
struct combinatorics{
	vector<T> inv, fact, invfact;
	vector<vector<T>> stir1, stir2;
	combinatorics(): inv(SZ << 1 | 1, 1), fact(SZ << 1 | 1, 1), invfact(SZ << 1 | 1, 1){
		for(int i = 1; i <= SZ << 1; ++ i) fact[i] = fact[i - 1] * i;
		invfact[SZ << 1] = 1 / fact[SZ << 1];
		for(int i = (SZ << 1) - 1; i >= 0; -- i){
			invfact[i] = invfact[i + 1] * (i + 1);
			inv[i + 1] = invfact[i + 1] * fact[i];
		}
	} // O(SZ)
	T C(int n, int k){ return n < k ? 0 : fact[n] * invfact[k] * invfact[n - k]; }
	T P(int n, int k){ return n < k ? 0 : fact[n] * invfact[n - k]; }
	T H(int n, int k){ return C(n + k - 1, k); }
	vector<T> precalc_power(int base, int n = SZ << 1){
		vector<T> res(n + 1, 1);
		for(int i = 1; i <= n; ++ i) res[i] = res[i - 1] * base;
		return res;
	}
	T naive_C(long long n, long long k){
		if(n < k) return 0;
		T res = 1;
		k = min(k, n - k);
		for(long long i = n; i > n - k; -- i) res *= i;
		return res * invfact[k];
	}
	T naive_P(long long n, int k){
		if(n < k) return 0;
		T res = 1;
		for(long long i = n; i > n - k; -- i) res *= i;
		return res;
	}
	T naive_H(long long n, long long k){ return naive_C(n + k - 1, k); }
	bool parity_C(long long n, long long k){ return n < k ? 0 : k & n - k ^ 1; }
	// Catalan's Trapzoids
	// # of bitstrings of n Xs and k Ys such that in each initial segment, (# of X) + m > (# of Y) 
	T Cat(int n, int k, int m = 1){
		if(m <= 0) return 0;
		else if(k >= 0 && k < m) return C(n + k, k);
		else if(k < n + m) return C(n + k, k) - C(n + k, k - m);
		else return 0;
	}
	// Stirling number
	// First kind (unsigned): # of n-permutations with k disjoint cycles
	//                        Also the coefficient of x^k for x_n = x(x+1)...(x+n-1)
	// Second kind: # of ways to partition a set of size n into r non-empty sets
	//              Satisfies sum{k=0~n}(x_k) = x^n
	array<bool, 2> pre{};
	template<bool FIRST = true>
	void precalc_stir(int n, int k){
		auto &s = FIRST ? stir1 : stir2;
		pre[!FIRST] = true;
		s.resize(n + 1, vector<T>(k + 1, 1));
		for(int i = 1; i <= n; ++ i) for(int j = 1; j <= k; ++ j){
			s[i][j] = (FIRST ? i - 1 : j) * s[i - 1][j] + s[i - 1][j - 1];
		}
	}
	// unsigned
	T Stir1(int n, int k){
		if(n < k) return 0;
		assert(pre[0]);
		return stir1[n][k];
	}
	T Stir2(long long n, int k){
		if(n < k) return 0;
		if(pre[1] && n < int(stir2.size())) return stir2[n][k];
		T res = 0;
		for(int i = 0, sign = 1; i <= k; ++ i, sign *= -1) res += sign * C(k, i) * (Zp(k - i) ^ n);
		return res * invfact[k];
	}
	bool parity_Stir2(long long n, long long k){ return n < k ? 0 : k ? !(n - k & k - 1 >> 1) : 0; }
};

// Requires modular
template<int root = 15311432, int root_pw = 1 << 23, int inv_root = 469870224, typename IT = vector<Zp>::iterator>
void number_theoric_transform(IT begin, IT end, const bool invert = false){
	int n = end - begin;
	for(int i = 1, j = 0; i < n; ++ i){
		int bit = n >> 1;
		for(; j & bit; bit >>= 1) j ^= bit;
		j ^= bit;
		if(i < j) swap(*(begin + i), *(begin + j));
	}
	for(int len = 1; len < n; len <<= 1){
		typename iterator_traits<IT>::value_type wlen = invert ? inv_root : root;
		for(int i = len << 1; i < root_pw; i <<= 1) wlen *= wlen;
		for(int i = 0; i < n; i += len << 1){
			typename iterator_traits<IT>::value_type w = 1;
			for(int j = 0; j < len; ++ j){
				auto u = *(begin + i + j), v = *(begin + i + j + len) * w;
				*(begin + i + j) = u + v;
				*(begin + i + j + len) = u - v;
				w *= wlen;
			}
		}
	}
	if(invert){
		auto inv_n = typename iterator_traits<IT>::value_type(1) / n;
		for(auto it = begin; it != end; ++ it) *it *= inv_n;
	}
}
const size_t magic_constant = 250;
template<typename Poly>
void convolute(Poly &a, Poly b){
	if(min(a.size(), b.size()) < magic_constant){
		Poly res((int)a.size() + (int)b.size() - 1);
		for(size_t i = 0; i < a.size(); ++ i) for(size_t j = 0; j < b.size(); ++ j) res[i + j] += a[i] * b[j];
		a = move(res);
		return;
	}
	int n = max((int)a.size() + (int)b.size() - 1, 1);
	if(__builtin_popcount(n) != 1) n = 1 << __lg(n) + 1;
	a.resize(n), b.resize(n);
	number_theoric_transform(a.begin(), a.end()), number_theoric_transform(b.begin(), b.end());
	for(int i = 0; i < n; ++ i) a[i] *= b[i];
	number_theoric_transform(a.begin(), a.end(), 1);
	while(!a.empty() && !a.back()) a.pop_back();
}

// DEBUG BEGIN
#ifdef LOCAL
template<typename L, typename R> ostream &operator<<(ostream &out, const pair<L, R> &p){
	return out << "(" << p.first << ", " << p.second << ")";
}
template<typename Tuple, size_t N> struct TuplePrinter{
	static ostream &print(ostream &out, const Tuple &t){ return TuplePrinter<Tuple, N-1>::print(out, t) << ", " << get<N-1>(t); }
};
template<typename Tuple> struct TuplePrinter<Tuple, 1>{
	static ostream &print(ostream &out, const Tuple& t){ return out << get<0>(t); }
};
template<typename... Args> ostream &print_tuple(ostream &out, const tuple<Args...> &t){
	return TuplePrinter<decltype(t), sizeof...(Args)>::print(out << "(", t) << ")";
}
template<typename ...Args> ostream &operator<<(ostream &out, const tuple<Args...> &t){
	return print_tuple(out, t);
}
template<typename T> ostream &operator<<(enable_if_t<!is_same<T, string>::value, ostream> &out, const T &arr){
	out << "{"; for(auto &x: arr) out << x << ", ";
	return out << (arr.size() ? "\b\b" : "") << "}";
}
template<size_t S> ostream &operator<<(ostream &out, const bitset<S> &b){
	for(int i = 0; i < S; ++ i) out << b[i];
	return out;
}
void debug_out(){ cerr << "\b\b " << endl; }
template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T){ cerr << H << ", ", debug_out(T...); }
void debug2_out(){ cerr << "-----DEBUG END-----\n"; }
template<typename Head, typename... Tail>
void debug2_out(Head H, Tail... T){ cerr << "\n"; for(auto x: H) cerr << x << "\n"; debug2_out(T...); }
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]: ", debug_out(__VA_ARGS__)
#define debug2(...) cerr << "----DEBUG BEGIN----\n[" << #__VA_ARGS__ << "]:", debug2_out(__VA_ARGS__)
#else
#define debug(...) 42
#define debug2(...) 42
#endif
// DEBUG END

int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(ios::badbit | ios::failbit);
	combinatorics<100000> C;
	auto invp = C.precalc_power((Zp(1) / 2).value);
	int n;
	cin >> n;
	const int mx = 1e5;
	vector<int> cnt(mx);
	for(auto i = 0; i < 2 * n; ++ i){
		int x;
		cin >> x, -- x;
		++ cnt[x];
	}
	auto calc = [&](int tot, int sub){
		assert(2 * sub <= tot);
		return C.fact[tot] * C.invfact[sub] * invp[sub] * C.invfact[tot - 2 * sub];
	};
	vector<vector<Zp>> poly(mx);
	priority_queue<array<int, 2>, vector<array<int, 2>>, greater<>> pq;
	for(auto i = 0; i < mx; ++ i){
		for(auto x = 0; x <= cnt[i] / 2; ++ x){
			poly[i].push_back(calc(cnt[i], x));
		}
		if((int)poly[i].size() > 1){
			pq.push({(int)poly.size(), i});
		}
	}
	while((int)pq.size() > 1){
		int i = pq.top()[1]; pq.pop();
		int j = pq.top()[1]; pq.pop();
		int k = (int)poly.size();
		poly.push_back(poly[i]);
		convolute(poly[k], poly[j]);
		pq.push({(int)poly[k].size(), k});
	}
	int i = pq.top()[1];
	debug(poly[9], poly[19], poly[29], poly[39], poly[49], poly[59]);
	debug(i, poly[i]);
	Zp res = 0;
	for(auto j = 0, sign = 1; j < (int)poly[i].size(); ++ j, sign = -sign){
		res += sign * calc(2 * n - 2 * j, n - j) * poly[i][j];
	}
	cout << res << "\n";
	return 0;
}

/*

*/

////////////////////////////////////////////////////////////////////////////////////////
//                                                                                    //
//                                   Coded by Aeren                                   //
//                                                                                    //
////////////////////////////////////////////////////////////////////////////////////////