#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
const int mod=1000000007;
struct edges
{
	int to,next;
}edge[10101];
int first[5050],now;
void adde(int x,int y)
{
	now++;
	edge[now].to=y;
	edge[now].next=first[x];
	first[x]=now;
}
int dp[5050][5050];
int h[5050];
int f[5050],siz[5050];
void work(int p,int fa)
{
	dp[p][1]=1;
	siz[p]=1;
	for(int e=first[p];e;e=edge[e].next)
		if(edge[e].to!=fa) 
		{
			work(edge[e].to,p);
			for(int i=0;i<=siz[p];i++)
			{
				f[i]=dp[p][i];
				dp[p][i]=0;
			}
			for(int i=0;i<=siz[p];i++)
				for(int j=0;j<=siz[edge[e].to];j++)
					dp[p][i+j]=((long long)f[i]*dp[edge[e].to][j]+dp[p][i+j])%mod;
			siz[p]+=siz[edge[e].to];
		}
	for(int i=1;i<=siz[p];i++)
		dp[p][0]=(dp[p][0]+mod-(long long)dp[p][i]*h[i]%mod)%mod;
}
int main()
{
	int n,u,v;
	scanf("%d",&n);
	for(int i=1;i<n;i++)
	{
		scanf("%d%d",&u,&v);
		adde(u,v);
		adde(v,u);
	}
	h[0]=1;
	for(int i=1;i<=n;i++)
		if(i&1)
			h[i]=0;
		else
			h[i]=(long long)h[i-2]*(i-1)%mod;
	memset(dp,0,sizeof(dp));
	work(1,0);
	printf("%d",(mod-dp[1][0]))%mod;
	return 0;
}