#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
#pragma GCC optimize ("-O3")
using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
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 (b<a) { a = b; return 1; } return 0; }
//---------------------------------------------------------------------------------------------------
template<int MOD> struct ModInt {
    static const int Mod = MOD; unsigned x; ModInt() : x(0) { }
    ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    int get() const { return (int)x; }
    ModInt &operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; }
    ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
    ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
    ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
    ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
    ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
    ModInt inverse() const { long long a = x, b = MOD, u = 1, v = 0;
        while (b) { long long t = a / b; a -= t * b; std::swap(a, b); u -= t * v; std::swap(u, v); }
        return ModInt(u); }
    bool operator==(ModInt that) const { return x == that.x; }
    bool operator!=(ModInt that) const { return x != that.x; }
    ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; }
};
template<int MOD> ostream& operator<<(ostream& st, const ModInt<MOD> a) { st << a.get(); return st; };
template<int MOD> ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k) {
    ModInt<MOD> r = 1; while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r; }
typedef ModInt<1000000007> mint;
/*---------------------------------------------------------------------------------------------------
　　　　　　　　　　　 ∧＿∧  
　　　　　 ∧＿∧ 　（´<_｀ ）　 Welcome to My Coding Space!
　　　　 （ ´_ゝ`）　/　 ⌒i     
　　　　／　　　＼　 　  |　|     
　　　 /　　 /￣￣￣￣/　　|  
　 ＿_(__ﾆつ/　    ＿/ .| .|＿＿＿＿  
　 　　　＼/＿＿＿＿/　（u　⊃  
---------------------------------------------------------------------------------------------------*/





int N;
vector<int> E[5010];
//---------------------------------------------------------------------------------------------------
mint comb[5010];
vector<vector<mint>> dp[5010];
void merge(int id0, int id1) {
    int sz0 = dp[id0][0].size();
    int sz1 = dp[id1][0].size();
    vector<vector<mint>> pd(2, vector<mint>(sz0 + sz1 - 1));

    rep(c0, 0, sz0) rep(p0, 0, 2) rep(c1, 0, sz1) rep(p1, 0, 2) {
        pd[(p0 + p1) % 2][c0 + c1] += dp[id0][p0][c0] * dp[id1][p1][c1];
        if (c1 % 2 == 0) pd[(p0 + p1 + 1) % 2][c0] += dp[id0][p0][c0] * dp[id1][p1][c1] * comb[c1];
    }

    swap(dp[id0], pd);
}
void dfs(int cu, int pa = -1) {
    dp[cu].push_back({ 0, 1 }); // dp[cu][0] := 頂点cuの部分木で使ってない辺が0本以上
    dp[cu].push_back({ 0, 0 }); // dp[cu][1] := 頂点cuの部分木で使ってない辺が1本以上

    fore(to, E[cu]) if (to != pa) {
        dfs(to, cu);
        merge(cu, to); //dp[cu] = dp[cu] + dp[to]
    }
}
//---------------------------------------------------------------------------------------------------
void _main() {
    cin >> N;
    rep(i, 0, N - 1) {
        int a, b;
        cin >> a >> b;
        a--; b--;
        E[a].push_back(b);
        E[b].push_back(a);
    }

    rep(i, 0, 5010) if (i % 2 == 0) {
        comb[i] = 1;
        int x = i - 1;
        while (1 < x) comb[i] *= mint(x), x -= 2;
    }
    dfs(0);

    mint ans = 0;
    rep(c, 0, dp[0][0].size()) if (c % 2 == 0) ans += dp[0][0][c] * comb[c];
    rep(c, 0, dp[0][0].size()) if (c % 2 == 0) ans -= dp[0][1][c] * comb[c];
    cout << ans << endl;
}

Measured memory_bytes: 70272