/*
ЗАПУСКАЕМ 
░ГУСЯ░▄▀▀▀▄░РАБОТЯГУ░░
▄███▀░◐░░░▌░░░░░░░
░░░░▌░░░░░▐░░░░░░░
░░░░▐░░░░░▐░░░░░░░
░░░░▌░░░░░▐▄▄░░░░░
░░░░▌░░░░▄▀▒▒▀▀▀▀▄
░░░▐░░░░▐▒▒▒▒▒▒▒▒▀▀▄
░░░▐░░░░▐▄▒▒▒▒▒▒▒▒▒▒▀▄
░░░░▀▄░░░░▀▄▒▒▒▒▒▒▒▒▒▒▀▄
░░░░░░▀▄▄▄▄▄█▄▄▄▄▄▄▄▄▄▄▄▀▄
░░░░░░░░░░░▌▌░▌▌░░░░░
░░░░░░░░░░░▌▌░▌▌░░░░░
░░░░░░░░░▄▄▌▌▄▌▌░░░░░ 
 */
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
#pragma GCC optimize("unroll-loops")  
#include <iostream>
#include <complex>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <numeric>
#include <cstring>
#include <ctime>
#include <cstdlib>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <list>
#include <cmath>
#include <bitset>
#include <cassert>
#include <queue>
#include <stack>
#include <deque>
     
      
using namespace std;
template<typename T1, typename T2>inline void chkmin(T1 &x, const T2 &y) { if (x > y) x = y; }
template<typename T1, typename T2>inline void chkmax(T1 &x, const T2 &y) { if (x < y) x = y; } 
template<typename T, typename U> inline ostream &operator<< (ostream &_out, const pair<T, U> &_p) { _out << _p.first << ' ' << _p.second; return _out; }
template<typename T, typename U> inline istream &operator>> (istream &_in, pair<T, U> &_p) { _in >> _p.first >> _p.second; return _in; }
template<typename T> inline ostream &operator<< (ostream &_out, const vector<T> &_v) { if (_v.empty()) { return _out; } _out << _v.front(); for (auto _it = ++_v.begin(); _it != _v.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline istream &operator>> (istream &_in, vector<T> &_v) { for (auto &_i : _v) { _in >> _i; } return _in; }
template<typename T> inline ostream &operator<< (ostream &_out, const set<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline ostream &operator<< (ostream &_out, const multiset<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline ostream &operator<< (ostream &_out, const unordered_set<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline ostream &operator<< (ostream &_out, const unordered_multiset<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T, typename U> inline ostream &operator<< (ostream &_out, const map<T, U> &_m) { if (_m.empty()) { return _out; } _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')'; for (auto _it = ++_m.begin(); _it != _m.end(); ++_it) { _out << ", (" << _it->first << ": " << _it->second << ')'; } return _out; }
template<typename T, typename U> inline ostream &operator<< (ostream &_out, const unordered_map<T, U> &_m) { if (_m.empty()) { return _out; } _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')'; for (auto _it = ++_m.begin(); _it != _m.end(); ++_it) { _out << ", (" << _it->first << ": " << _it->second << ')'; } return _out; }
#define sz(c) (int)(c).size()
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define left left228
#define right right228
#define rank rank228
#define y1 y1228                                                         
#define read(FILENAME) freopen(((string)FILENAME + ".in").c_str(), "r", stdin)
#define write(FILENAME) freopen(((string)FILENAME + ".out").c_str(), "w", stdout)
#define files(FILENAME) read(FILENAME), write(FILENAME)
#define pb push_back
const int MAXN = 5005;
const int M = 1000000007;


int n;
long long dp[MAXN][MAXN][2], temp[MAXN][2], fact[MAXN], sz[MAXN];
long long ans;
vector<int> g[MAXN];


void add(long long &a,long long b){
    a+=b;
    if(a >= M)a-=M;
    if(a < 0)a+=M;
}


void calc(int u,int p){
    dp[u][1][0] = 1;
    sz[u] = 1;
    for(auto i : g[u])
        if(i != p){
            calc(i,u);
            for(int j = 0;j <= sz[u];j++)
                for(int k = 0;k < 2;k++)
                    temp[j][k] = dp[u][j][k],
                    dp[u][j][k] = 0;
            for(int j = 1;j <= sz[u];j++)
                for(int k = 1;k <= sz[i];k++)
                    for(int a = 0;a < 2;a++)
                        for(int b = 0;b < 2;b++){
                            add(dp[u][j + k][a^b],temp[j][a]*1LL*dp[i][k][b]%M);
                            if(!(k&1))add(dp[u][j][a^b^1],(temp[j][a]*1LL*dp[i][k][b]%M)*fact[k]%M);
                        }
            sz[u]+=sz[i];
        }
}



int main() {
    ios_base::sync_with_stdio(false);
    cout.tie(0);
 //   read("input");
    cin >> n;
    for (int i = 0; i < n - 1; i++) {
        int a, b;
        cin >> a >> b;
        a--, b--;
        g[a].pb(b);
        g[b].pb(a);
    }
    fact[0] = 1;
    for(int i = 2;i < MAXN;i+=2)fact[i] = (i - 1LL)*fact[i - 2]%M;
        calc(0,-1);
    for(int i = 2;i <= n;i+=2)add(ans,fact[i]*1LL*(dp[0][i][0] - dp[0][i][1])%M);
    cout << ans << '\n';
}



Measured memory_bytes: 391424