using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using SB = System.Text.StringBuilder;
using System.Numerics;
using static System.Math;
using Point = System.Numerics.Complex;
using Number = System.Int64;
namespace Program {
    public class Solver {
        Random rnd = new Random(0);
        public void Solve() {
            var n = ri;
            G = Enumerate(n, x => new List<int>());
            for (int i = 0; i < n - 1; i++)
            {
                var u = ri - 1;
                var v = ri - 1;
                G[u].Add(v);
                G[v].Add(u);
            }

            if (false)
            {
                n = 5000;
                G = Enumerate(n, x => new List<int>());
                for (int i = 1; i < n; i++)
                {
                    var p = rnd.Next() % i;
                    G[p].Add(i);
                    G[i].Add(p);
                }
            }
            coef = new ModInt[n + 1];
            coef[0] = 1;
            for (int i = 2; i <= n; i += 2)
                coef[i] = coef[i - 2] * (i - 1);
            dp = Enumerate(n, x => new long[0]);
            ep = Enumerate(n, x => new long[0]);
            dfs(-1, 0);
            ModInt ans = 0;
            for (int i = 0; i <= n; i += 2)
            {
                ans += dp[0][i] * coef[i];
                ans -= ep[0][i] * coef[i];
            }
            Console.WriteLine(ans);

        }
        ModInt[] coef;
        long[][] dp;
        long[][] ep;
        int dfs(int prev, int cur) {
            var ret = 1;
            var u = new long[2];
            var v = new long[2];
            u[1] = 1;
            foreach (var to in G[cur])
            {
                if (prev == to) continue;
                ret += dfs(cur, to);
                var nu = new long[ret + 1];
                var nv = new long[ret + 1];
                var p = dp[to];
                var q = ep[to];
                for (int i = 0; i < u.Length; i++)
                {
                    for (int j = 0; j < dp[to].Length; j++)
                    {

                        nu[i + j] += u[i] * p[j] + v[i] * q[j];
                        nv[i + j] += u[i] * q[j] + v[i] * p[j];
                        if (j % 2 == 0)
                        {
                            nu[i] += ((u[i] * q[j] + v[i] * p[j]) % ModInt.Mod * coef[j].num) % ModInt.Mod;
                            nv[i] += ((u[i] * p[j] + v[i] * q[j]) % ModInt.Mod * coef[j].num) % ModInt.Mod;
                        }
                        nu[i + j] %= ModInt.Mod;
                        nv[i + j] %= ModInt.Mod;
                    }
                    nu[i] %= ModInt.Mod;
                    nv[i] %= ModInt.Mod;
                }
                u = nu;
                v = nv;
            }
            dp[cur] = u;
            ep[cur] = v;
            return ret;
        }
        List<int>[] G;
        const long INF = 1L << 60;
        int ri { get { return sc.Integer(); } }
        long rl { get { return sc.Long(); } }
        double rd { get { return sc.Double(); } }
        string rs { get { return sc.Scan(); } }
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());

        static T[] Enumerate<T>(int n, Func<int, T> f) {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f(i);
            return a;
        }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex {
    static public string AsString(this IEnumerable<char> ie) { return new string(ie.ToArray()); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") {
        return string.Join(st, ie);
    }
    static public void Main() {
        Console.SetOut(new Program.IO.Printer(Console.OpenStandardOutput()) { AutoFlush = false });
        var solver = new Program.Solver();
        solver.Solve();
        Console.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO {
    using System.IO;
    using System.Text;
    using System.Globalization;

    public class Printer: StreamWriter {
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
    }

    public class StreamScanner {
        public StreamScanner(Stream stream) { str = stream; }

        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }

        private byte read() {
            if (isEof) return 0;
            if (ptr >= len)
            {
                ptr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0)
                {
                    isEof = true;
                    return 0;
                }
            }
            return buf[ptr++];
        }

        public char Char() {
            byte b = 0;
            do b = read(); while ((b < 33 || 126 < b) && !isEof);
            return (char)b;
        }
        public string Scan() {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine() {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n' && b != 0; b = (char)read()) if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long() { return isEof ? long.MinValue : long.Parse(Scan()); }
        public int Integer() { return isEof ? int.MinValue : int.Parse(Scan()); }
        public double Double() { return isEof ? double.NaN : double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
}

#endregion

#region ModInt
public struct ModInt {
    public const long Mod = (long)1e9 + 7;
    public long num;
    public ModInt(long n) { num = n; }
    public override string ToString() { return num.ToString(); }
    public static ModInt operator +(ModInt l, ModInt r) { l.num += r.num; if (l.num >= Mod) l.num -= Mod; return l; }
    public static ModInt operator -(ModInt l, ModInt r) { l.num -= r.num; if (l.num < 0) l.num += Mod; return l; }
    public static ModInt operator *(ModInt l, ModInt r) { return new ModInt(l.num * r.num % Mod); }
    public static implicit operator ModInt(long n) { n %= Mod; if (n < 0) n += Mod; return new ModInt(n); }
    public static ModInt Pow(ModInt v, long k) { return Pow(v.num, k); }
    public static ModInt Pow(long v, long k) {
        long ret = 1;
        for (k %= Mod - 1; k > 0; k >>= 1, v = v * v % Mod)
            if ((k & 1) == 1) ret = ret * v % Mod;
        return new ModInt(ret);
    }
    public static ModInt Inverse(ModInt v) { return Pow(v, Mod - 2); }
}
#endregion

Measured memory_bytes: 168940