//tree DP
//ABC036-D
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<stdbool.h>
#include<time.h>
#define inf 1072114514
#define llinf 4154118101919364364
#define mod 1000000007
#define pi 3.1415926535897932384

int max(int a,int b){if(a>b){return a;}return b;}
int min(int a,int b){if(a<b){return a;}return b;}
int zt(int a,int b){return max(a,b)-min(a,b);}
int round(int a,int b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
int ceil(int a,int b){if(a%b==0){return a/b;}return (a/b)+1;}
int gcd(int a,int b){int c;while(b!=0){c=a%b;a=b;b=c;}return a;}
int lcm(int a,int b){int c=gcd(a,b);a/=c;return a*b;}
int nCr(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
int nHr(int a,int b){return nCr(a+b-1,b);}
int fact(int a){int i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
int pow(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
int dsum(int x){int r=0;while(x){r+=(x%10);x/=10;}return r;}
int dsumb(int x,int b){int r=0;while(x){r+=(x%b);x/=b;}return r;}
int sankaku(int x){return ((1+x)*x)/2;}
void swap(int *a,int *b){int c;c=(*a);(*a)=(*b);(*b)=c;}
long long llmax(long long a,long long b){if(a>b){return a;}return b;}
long long llmin(long long a,long long b){if(a<b){return a;}return b;}
long long llzt(long long a,long long b){return llmax(a,b)-llmin(a,b);}
long long llround(long long a,long long b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
long long llceil(long long a,long long b){if(a%b==0){return a/b;}return (a/b)+1;}
long long llgcd(long long a,long long b){long long c;while(b!=0){c=a%b;a=b;b=c;}return a;}
long long lllcm(long long a,long long b){long long c=llgcd(a,b);a/=c;return a*b;}
long long llnCr(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
long long llnHr(long long a,long long b){return llnCr(a+b-1,b);}
long long llfact(long long a){long long i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
long long llpow(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
long long lldsum(long long x){long long r=0;while(x){r+=(x%10);x/=10;}return r;}
long long lldsumb(long long x,long long b){long long r=0;while(x){r+=(x%b);x/=b;}return r;}
long long llsankaku(long long x){return ((1+x)*x)/2;}
void llswap(long long *a,long long *b){long long c;c=(*a);(*a)=(*b);(*b)=c;}
double dbmax(double a,double b){if(a>b){return a;}return b;}
double dbmin(double a,double b){if(a<b){return a;}return b;}
double dbzt(double a,double b){return dbmax(a,b)-dbmin(a,b);}
void dbswap(double *a,double *b){double c;c=(*a);(*a)=(*b);(*b)=c;}
void chswap(char *a,char *b){char c;c=(*a);(*a)=(*b);(*b)=c;}
int sortfncsj(const void *a,const void *b){if(*(int *)a>*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int sortfnckj(const void *a,const void *b){if(*(int *)a<*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int llsortfncsj(const void *a,const void *b){if(*(long long *)a>*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int llsortfnckj(const void *a,const void *b){if(*(long long *)a<*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int dbsortfncsj(const void *a,const void *b){if(*(double *)a>*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int dbsortfnckj(const void *a,const void *b){if(*(double *)a<*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int strsortfncsj(const void *a,const void *b){return strcmp((char *)a,(char *)b);}
int strsortfnckj(const void *a,const void *b){return strcmp((char *)b,(char *)a);}
int chsortfncsj(const void *a,const void *b){if(*(char *)a>*(char *)b){return 1;}if(*(char *)a==*(char *)b){return 0;}return -1;}
int chsortfnckj(const void *a,const void *b){if(*(char *)a<*(char *)b){return 1;}if(*(char *)a==*(char *)b){return 0;}return -1;}

typedef struct{
int val;
int node;
}sd;

int sdsortfnc(const void *a,const void *b){
if(((sd*)a)->val > ((sd*)b)->val){return -1;}
if(((sd*)a)->val < ((sd*)b)->val){return 1;}
return 0;
}

typedef struct{
    long long st;
    long long fi;
    long long kr;
}rs;

typedef struct{
    long long st;
    long long kz;
}mkj;

int sortfnc(const void *a,const void *b){
if(((rs*)a)->st > ((rs*)b)->st){return 1;}
if(((rs*)a)->st < ((rs*)b)->st){return -1;}
return 0;
}

void makemkj(rs g[],mkj x[],long long n){
    long long i,ms=0,nst=g[0].st;
    for(i=1;i<n;i++){
        if(g[i].st!=g[i-1].st){
            x[nst].kz=i-ms;
            x[nst].st=ms;
            nst=g[i].st;ms=i;
        }
    }
    x[nst].kz=n-ms;
    x[nst].st=ms;
}

long long dist[524288],par[524288];
void dfs(long long t,long long l,long long bp,rs g[],mkj x[]){
  long long i;
  if(dist[t]<=l){return;}
  dist[t]=l;
  par[t]=bp;
  for(i=x[t].st;i<x[t].st+x[t].kz;i++){
    dfs(g[i].fi,l+1,t,g,x);
  }
}

int main(void){
  long long i,j,n,m,k,a,b,c,h,w,r=0,l,t,p,q;
  long long bp,bq;
  long long ***dp=malloc(sizeof(long long**)*5005);
  for(i=0;i<5005;i++){
    dp[i]=malloc(sizeof(long long*)*5005);
    for(j=0;j<5005;j++){
      dp[i][j]=malloc(sizeof(long long)*2);
      dp[i][j][0]=0;
      dp[i][j][1]=0;
    }
  }
  long long ndp[5005][2]={0};
  long long wei[524288]={0};
  rs g[524288];
  mkj x[524288];
  sd dat[524288];
  long long f[8192]={0};
  f[0]=1;
  for(i=2;i<8192;i+=2){
    f[i]=((i-1)*f[i-2])%mod;
  }
  scanf("%lld",&n);
  for(i=0;i<(n-1);i++){
    scanf("%lld%lld",&a,&b);
    g[2*i].st=a;
    g[2*i].fi=b;
    g[2*i].kr=1;
    g[2*i+1].st=b;
    g[2*i+1].fi=a;
    g[2*i+1].kr=1;
  }
  qsort(g,2*(n-1),sizeof(g[0]),sortfnc);
  makemkj(g,x,2*(n-1));
  for(i=0;i<=n;i++){
    dist[i]=inf;
  }
  dfs(1,0,-1,g,x);
  for(i=0;i<n;i++){
    dat[i].node=i+1;
    dat[i].val=dist[i+1];
  }
  qsort(dat,n,sizeof(dat[0]),sdsortfnc);
  for(i=0;i<n;i++){
    w=dat[i].node;
    dp[w][1][0]=1;
    wei[w]++;
    for(j=x[w].st;j<x[w].st+x[w].kz;j++){
      if(par[w]==g[j].fi){continue;}
      for(p=1;p<=wei[w];p++){
        for(q=1;q<=wei[g[j].fi];q++){
          for(bp=0;bp<2;bp++){
            for(bq=0;bq<2;bq++){
              t=(bp+bq+1)%2;
              k=dp[g[j].fi][q][bq];
              k*=f[q];k%=mod;
              k*=dp[w][p][bp];k%=mod;
              ndp[p][t]=(ndp[p][t]+k)%mod;
              t=(bp+bq)%2;
              k=dp[g[j].fi][q][bq];
              k*=dp[w][p][bp];k%=mod;
              ndp[p+q][t]=(ndp[p+q][t]+k)%mod;
            }
          }
        }
      }
      wei[w]+=wei[g[j].fi];
      for(p=1;p<=wei[w];p++){
        for(q=0;q<2;q++){
          dp[w][p][q]=ndp[p][q];
          ndp[p][q]=0;
        }
      }
    }
  }
  for(i=2;i<=n;i+=2){
    r=(r+dp[1][i][0]*f[i])%mod;
    r=(r+mod-((dp[1][i][1]*f[i])%mod))%mod;
  }
  printf("%lld\n",r);
  return 0;
}


Measured memory_bytes: 995472