#include <iostream>
#include <vector>

using namespace std;

typedef long long ll;

const int MOD = 1e9 + 7; // change if needed

struct Modint {
  ll val;
  
  Modint (ll _val = 0)
    : val(_val % MOD) {}

  Modint operator+ (Modint other) const {
    return Modint(val + other.val);
  }

  void operator+= (Modint other) {
    val += other.val;
    val %= MOD;
  }

  Modint operator- () const {
    return Modint(MOD - val);
  }

  Modint operator- (Modint other) const {
    return Modint(val + MOD - other.val);
  }

  void operator-= (Modint other) {
    val += MOD - other.val;
    val %= MOD;
  }

  Modint operator* (Modint other) const {
    return Modint(val * other.val);
  }

  void operator*= (Modint other) {
    val *= other.val;
    val %= MOD;
  }

  bool operator== (Modint other) const {
    return val == other.val;
  }

  bool operator!= (Modint other) const {
    return val != other.val;
  }
};

Modint exp (Modint a, int k) {
  if (k == 0) {
    return Modint(1);
  } else if (k % 2 == 0) {
    Modint half = exp(a, k / 2);
    return half * half;
  } else {
    return a * exp(a, k - 1);
  }
}

Modint inv (Modint a) {
  return exp(a, MOD - 2);
}

ostream& operator<< (ostream& out, Modint p) {
  out << p.val;
  return out;
}

const int MAX_N = 5e3 + 5;

Modint fact [2 * MAX_N];
Modint invfact [2 * MAX_N];
Modint itpow [2 * MAX_N];

Modint ways (int a) {
  return fact[a] * invfact[a / 2] * itpow[a / 2];
}

vector<int> adj [MAX_N];

vector<Modint> dp0 [MAX_N];
vector<Modint> dp1 [MAX_N];

void dfs (int u, int p) {
  vector<Modint> cur0 = {0, 1};
  vector<Modint> cur1 = {0, 0};
  
  for (int nxt : adj[u]) {
    if (nxt != p) {
      dfs(nxt, u);

      vector<Modint> nxt0 (max((int) cur0.size() + (int) dp0[nxt].size() - 1,
                            (int) cur1.size() + (int) dp1[nxt].size() - 1), Modint(0));
      vector<Modint> nxt1 (max((int) cur0.size() + (int) dp1[nxt].size() - 1,
                            (int) cur1.size() + (int) dp0[nxt].size() - 1), Modint(0));

      for (int i = 0; i < (int) cur0.size(); i++) {
        for (int j = 0; j < (int) dp0[nxt].size(); j++) {
          nxt0[i + j] += cur0[i] * dp0[nxt][j];
        }

        for (int j = 0; j < (int) dp1[nxt].size(); j++) {
          nxt1[i + j] += cur0[i] * dp1[nxt][j];
        }
      }

      for (int i = 0; i < (int) cur1.size(); i++) {
        for (int j = 0; j < (int) dp0[nxt].size(); j++) {
          nxt1[i + j] += cur1[i] * dp0[nxt][j];
        }

        for (int j = 0; j < (int) dp1[nxt].size(); j++) {
          nxt0[i + j] += cur1[i] * dp1[nxt][j];
        }
      }

      cur0 = nxt0;
      cur1 = nxt1;
    }
  }

  dp0[u] = cur0;
  dp1[u] = cur1;
  for (int i = 2; i < (int) dp1[u].size(); i += 2) {
    dp0[u][0] += dp1[u][i] * ways(i);
  }
  for (int i = 2; i < (int) dp0[u].size(); i += 2) {
    dp1[u][0] += dp0[u][i] * ways(i);
  }
}

int main () {
  ios::sync_with_stdio(false);

  fact[0] = 1;
  invfact[0] = 1;
  itpow[0] = 1;
  Modint in2 = inv(Modint(2));
  for (int i = 1; i < 2 * MAX_N; i++) {
    fact[i] = fact[i - 1] * i;
    invfact[i] = invfact[i - 1] * inv(Modint(i));
    itpow[i] = itpow[i - 1] * in2;
  }
  
  int n;
  cin >> n;

  for (int i = 0; i < n - 1; i++) {
    int u, v;
    cin >> u >> v;

    adj[u].push_back(v);
    adj[v].push_back(u);
  }

  dfs(1, 0);

  cout << dp1[1][0] - dp0[1][0] << endl;
}


Measured memory_bytes: 139136