// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define bit(n) (1LL<<(n))
// functions
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

ll g[5010];
vector<int> edge[5010], child[5010];
int s[5010];

void dfs(int i, int p){
  s[i] = 1;
  for(auto e: edge[i]){
    if(e == p)continue;
    child[i].pb(e);
    dfs(e, i);
    s[i] += s[e];
  }
}

ll dp[5010][5010][2], dp2[5010][5010][2];

void calc(int v){
  if(sz(child[v]) == 0){
    dp[v][1][0] = 1;
    return;
  }
  for(auto e: child[v])calc(e);
  int cs = 1;
  dp2[0][1][0] = 1;
  int idx = 0;
  for(auto e: child[v]){
    cs += s[e];
    rep(i, cs + 1)dp2[idx+1][i][0] = 0;
    rep(i, cs + 1)dp2[idx+1][i][1] = 0;
    for(int j = 0; j <= cs - s[e]; j++){
      for(int k = 0; k <= s[e]; k++){
        rep(l, 2){
          rep(m, 2){
            if(k % 2 == 0){
              (dp2[idx+1][j][(l+m+1)&1] += (dp2[idx][j][l] * dp[e][k][m] % mod) * g[k] % mod) %= mod;
            }
            (dp2[idx+1][j+k][(l+m)&1] += (dp2[idx][j][l] * dp[e][k][m] % mod)) %= mod;
          }
        }
      }
    }
    idx++;
  }
  rep(i, cs + 1){
    dp[v][i][0] = dp2[idx][i][0];
    dp[v][i][1] = dp2[idx][i][1];
  }
}

int main(int argc, char const* argv[])
{
  int n; cin >> n;
  rep(i, n - 1){
    int x, y; cin >> x >> y, x--, y--;
    edge[x].pb(y);
    edge[y].pb(x);
  }
  dfs(0, -1);
  g[0] = 1;
  FOR(i, 2, n + 1){
    if(i & 1)continue;
    g[i] = g[i-2] * (i - 1) % mod;
  }
  calc(0);
  /*rep(i, n){
    rep(j, s[i] + 1){
      //cout << i << " " << j << " 0 " << dp[i][j][0] << endl;
      //cout << i << " " << j << " 1 " << dp[i][j][1] << endl;
    }
  }*/
  ll res = 0;
  FOR(i, 1, n + 1){
    (res += dp[0][i][0] * g[i] % mod) %= mod;
    (res -= dp[0][i][1] * g[i] % mod) %= mod;
  }
  if(res < 0)res += mod;
  cout << res << endl;
  return 0;
}


Measured memory_bytes: 783360