#include <cstdio>
#include <cstring>
#include <set>
#include <map>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;

namespace my
{
	//-----------------------------------------------------------------------------
	inline char cn()
	{
		static char buf[1000010],*p1=buf,*p2=buf;
		return p1==p2&&(p2=(p1=buf)+fread(buf,1,1000000,stdin),p1==p2)?EOF:*p1++;
	}
	#define cn getchar
	template<class TY>void read(TY &x)
	{
		x=0;int f1=1;char ch=cn();
		while(ch<'0'||ch>'9'){if(ch=='-')f1=-1;ch=cn();}
		while(ch>='0'&&ch<='9')x=x*10+(ch-'0'),ch=cn(); x*=f1;
	}
	char Output[1000100],Zk[100];int op_top=0,Zk_top;
	void fcheck(int Type=0){if(Type||op_top>=1000000)fwrite(Output,1,op_top,stdout),op_top=0;}
	template<class TY>inline void write(TY x)
	{
		if(x==0){Output[op_top++]='0';fcheck();return;}
		if(x<0)Output[op_top++]='-',x=-x;
		Zk_top=0;while(x)Zk[++Zk_top]=x%10+'0',x/=10;
		while(Zk_top)Output[op_top++]=Zk[Zk_top--];fcheck();
	}
	#define K_G Output[op_top++]=' '
	#define H_C Output[op_top++]='\n'
	//--------------------------------------------------------------------------------------------
	
	//--------------------------------------------------------------------------------------------
	#define ll long long
	#define uint unsigned int
	#define ull unsigned long long
	#define db double
	#define pb push_back
	#define INV(x) ksm(x,mod-2)
	#define inf 999999999
	#define mod 998244353
	
	void add(int &x,int y){x=(x+y>=mod?x+y-mod:x+y);}
	void dec(int &x,int y){x=(x-y<0?x-y+mod:x-y);}
	template<class TY>TY add(TY x){return x>=mod?x-mod:x;}
	template<class TY>TY dec(TY x){return x<0?x+mod:x;}
	template<class TY>void chkmin(TY &x,TY y){if(y<x)x=y;}
	template<class TY>void chkmax(TY &x,TY y){if(y>x)x=y;}
	//
	int ksm(int x,int y){int re=1;for(;(y&1?re=1ll*re*x%mod:0),y;y>>=1,x=1ll*x*x%mod);return re;}
	template<class TY>void discretization(TY *arr,int St,int Ed){
		vector<TY>Arr;Arr.clear();
		for(int i=St;i<=Ed;i++)Arr.push_back(arr[i]);
		sort(Arr.begin(),Arr.end());
		for(int i=St;i<=Ed;i++)arr[i]=lower_bound(Arr.begin(),Arr.end(),arr[i])-Arr.begin()+1;
	}
	//-----------------------------------------------------------------------------------------------
	
	//----------------------------------------------------------------------------------------------- 
	#define maxn 200010
	#define mod 998244353
	int n,a[maxn],b[maxn],f[maxn],tmp[maxn];//f[i]:at least i pairs are same
	int fac[maxn],inv[maxn],inv_fac[maxn];
	void FacInit(){
		fac[0]=inv_fac[0]=inv[1]=1;
		for(int i=1;i<=n;i++)fac[i]=1ll*fac[i-1]*i%mod;
		for(int i=2;i<=n;i++)inv[i]=1ll*(mod-mod/i)*inv[mod%i]%mod;
		for(int i=1;i<=n;i++)inv_fac[i]=1ll*inv_fac[i-1]*inv[i]%mod;
	}
	int C(int x,int y){
		if(x<y||y<0)return 0;
		return 1ll*fac[x]*inv_fac[y]%mod*inv_fac[x-y]%mod;
	}
	const int inv2=(mod+1)/2;
	int d[maxn];
	
	void main()
	{
		read(n);n<<=1;FacInit();
		for(int i=1;i<=n;i++)read(a[i]),b[a[i]]++;
		f[0]=1;int ma=0;
		d[0]=1;for(int i=2,in=inv2;i<=n;i+=2,in=1ll*in*inv2%mod)d[i]=1ll*fac[i]*in%mod*inv_fac[i/2]%mod;
		for(int i=1;i<=100000;i++)if(b[i]>1){
			for(int j=1;j<=b[i]/2;j++){
				int p=1ll*C(b[i],j*2)*d[2*j]%mod;
				for(int k=0;k<=ma;k++){
					add(tmp[k+j],1ll*f[k]*p%mod);
				}
			}
			ma+=b[i]/2;
			for(int j=0;j<=ma;j++)add(f[j],tmp[j]),tmp[j]=0;
		}
		int ans=0;
		for(int i=0;i<=ma;i++){
			if(i&1)dec(ans,1ll*f[i]*d[n-2*i]%mod);
			else add(ans,1ll*f[i]*d[n-2*i]%mod);
		}
		write(ans);
		fcheck(1);return;
	}
}

int main(){my::main();return 0;}

Measured memory_bytes: 4280