#include<bits/stdc++.h>

using namespace std;
//#define int long long
#define ll long long
#define db double
const int mod = 998244353;
const int N =4e3+ 10;
const double eps = 1e-10;

inline void read(int &a) {
    int s = 0, w = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if (ch == '-')
            w = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') {
        s = s * 10 + ch - '0';
        ch = getchar();
    }
    a = s * w;
}

void qw(int out) {
    if (out > 9)qw(out / 10);
    putchar(out % 10 | 48);
}
vector<vector<int>>q;
int dp[N][N/2][2];
int dp2[N/2][2];
int siz[N];
void dfs(int u,int fa){
    for(int i=0;i<q[u].size();i++){
        int y=q[u][i];
        if(y==fa)continue;
        dfs(y,u);
        siz[u]+=siz[y];
    }
}
void dfs2(int u,int fa){
    dp[u][0][0]=1;
    siz[u]=1;
    for(int i=0;i<q[u].size();i++){
        int y=q[u][i];
        if(y==fa)continue;
        dfs2(y,u);
        memset(dp2,0,sizeof dp2);
        for(int j=0;j<=siz[u]/2;j++){
            for(int k=0;k<=siz[y]/2;k++){
                dp2[j+k][0]+=((dp[y][k][0]+dp[y][k][1])%mod*dp[u][j][0])%mod;
                dp2[j+k][0]%=mod;
                dp2[j+k][1]+=((dp[y][k][0]+dp[y][k][1])%mod*dp[u][j][1])%mod;
                dp2[j+k][1]%=mod;
                dp2[j+k+1][1]+=((dp[y][k][0])%mod*dp[u][j][0])%mod;
                dp2[j+k+1][1]%=mod;
            }
        }
        for(int j=0;j<=siz[u]/2+siz[y]/2+1;j++){
            dp[u][j][0]=dp2[j][0];
            dp[u][j][1]=dp2[j][1];
        }
        siz[u]+=siz[y];
    }
}
void solve() {
  int n;
  cin>>n;
  q=vector<vector<int>>(2*n+5);
  for(int i=1,a,b;i<=2*n-1;i++){
      cin>>a>>b;
      q[a].push_back(b);
      q[b].push_back(a);
  }
  dfs(1,0);
    dfs2(1,0);
    vector<int>fac(2*n+5);
    fac[0]=1;
    fac[2]=1;
    for(int i=4;i<=2*n;i+=2){
        fac[i]=(fac[i-2]*(i-1))%mod;
    }
    int ans=fac[2*n];
    for(int i=1;i<=n;i++){
        if(i%2==1){
            ans-=((dp[1][i][0]+dp[1][i][1])%mod*fac[2*n-2*i])%mod;
            ans%=mod;
            ans+=mod;
            ans%=mod;
        }else{
            ans+=((dp[1][i][0]+dp[1][i][1])%mod*fac[2*n-2*i])%mod;
            ans%=mod;
            ans+=mod;
            ans%=mod;
        }
    }
    cout<<ans<<'\n';

}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    // cout<<fixed<<setprecision(10);
    //  cin >> T;
    while (T--)solve();
    return 0;
}