#include <algorithm>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <vector>
using namespace std;
using ll = long long;
#define fst first
#define snd second

/* clang-format off */
template <class T, size_t D> struct _vec { using type = vector<typename _vec<T, D - 1>::type>; };
template <class T> struct _vec<T, 0> { using type = T; };
template <class T, size_t D> using vec = typename _vec<T, D>::type;
template <class T> vector<T> make_v(size_t size, const T& init) { return vector<T>(size, init); }
template <class... Ts> auto make_v(size_t size, Ts... rest) { return vector<decltype(make_v(rest...))>(size, make_v(rest...)); }
/* clang-format on */

template <std::uint_fast64_t Modulus>
class modint {
  using u64 = std::uint_fast64_t;

 public:
  u64 a;

  constexpr modint(const u64 x = 0) noexcept
      : a(x % Modulus) {
  }
  constexpr u64 &value() noexcept {
    return a;
  }
  constexpr const u64 &value() const noexcept {
    return a;
  }
  constexpr modint operator+(const modint rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint operator-(const modint rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint operator*(const modint rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint operator/(const modint rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint &operator+=(const modint rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus) {
      a -= Modulus;
    }
    return *this;
  }
  constexpr modint &operator-=(const modint rhs) noexcept {
    if (a < rhs.a) {
      a += Modulus;
    }
    a -= rhs.a;
    return *this;
  }
  constexpr modint &operator*=(const modint rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint &operator/=(const modint rhs) noexcept {
    return *this *= ~rhs;
  }
  constexpr modint operator^(u64 exp) const noexcept {
    modint v = 1, x = *this;
    while (exp) {
      if (exp & 1) {
        v *= x;
      }
      x *= x;
      exp >>= 1;
    }
    return v;
  }
  constexpr modint operator~() const noexcept {
    return *this ^ (Modulus - 2);
  }
};

using mint = modint<1000000007>;

int main() {
  int N;
  while (cin >> N) {
    vec<int, 2> G(N);
    for (int i = 0; i < N - 1; i++) {
      int x, y;
      cin >> x >> y;
      --x;
      --y;
      G[x].push_back(y);
      G[y].push_back(x);
    }
    vector<mint> g(N + 1, mint(0));
    g[0] = 1;
    for (int i = 2; i <= N; i += 2) g[i] = g[i - 2] * (i - 1);
    auto clear = [&](vector<mint>& dp, int sz) {
      fill(dp.begin(), dp.begin() + 2 * (sz + 1), mint(0));
    };
    auto dfs = [&](auto f, int v, int p, int& sz) -> vector<mint> {
      auto cur = make_v(2 * (N + 1), mint(0));
      auto nxt = cur;
      sz = 1;
      clear(cur, sz);
      cur[1 * 2 + 0] = 1;
      for (int u : G[v]) {
        if (u == p) continue;
        int chsz;
        auto ch = f(f, u, v, chsz);
        clear(nxt, sz + chsz);
        for (int i = 1; i <= sz; i++) {
          for (int ip = 0; ip < 2; ip++) {
            for (int j = 1; j <= chsz; j++) {
              for (int jp = 0; jp < 2; jp++) {
                // 繋げる
                nxt[(i + j) * 2 + (ip + jp) % 2] += cur[i * 2 + ip] * ch[j * 2 + jp];
                // 繋げない
                nxt[i * 2 + (ip + jp + 1) % 2] += cur[i * 2 + ip] * ch[j * 2 + jp] * g[j];
              }
            }
          }
        }
        swap(cur, nxt);
        sz += chsz;
      }
      return cur;
    };
    int sz;
    auto dp = dfs(dfs, 0, -1, sz);
    mint res;
    for (int i = 1; i <= N; i++) {
      for (int ip = 0; ip < 2; ip++) {
        mint ways = dp[i * 2 + ip] * g[i];
        if (ip % 2 == 0) {
          res = res + ways;
        } else {
          res = res - ways;
        }
      }
    }
    cout << res.value() << endl;
  }
  return 0;
}


Measured memory_bytes: 638848