// ${url}
//
#![allow(unused_imports)]
use std::io::*;
use std::fmt::*;
use std::str::*;
use std::cmp::*;
use std::collections::*;

macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};

    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };

    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };

    ($iter:expr, [ next / $t:tt ]) => {
        {
            let len = read_value!($iter, usize);
            (0..len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
        }
    };

    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };

    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };

    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

#[allow(unused_macros)]
macro_rules! dvec {
    ($t:expr ; $len:expr) => {
        vec![$t; $len]
    };

    ($t:expr ; $len:expr, $($rest:expr),*) => {
        vec![dvec!($t; $($rest),*); $len]
    };
}

#[allow(unused_macros)]
macro_rules! ifv {
    ($t:expr, $a:expr, $b: expr) => {
        if $t { $a } else { $b }
    }
}

#[allow(unused_macros)]
macro_rules! fill {
    ($t:expr, $v:expr) => {
        for i in 0..$t.len() {
            $t[i] = $v;
        }
    };
}

#[allow(unused_macros)]
macro_rules! join {
    ($t:expr, $glue:expr) => {
        $t.into_iter().map(|w| w.to_string()).collect::<Vec<_>>().join($glue)
    };
}

#[allow(unused_macros)]
macro_rules! debug {
    ($($a:expr),*) => {
        println!(concat!($(stringify!($a), " = {:?}, "),*), $($a),*);
    }
}

fn merge(a: Vec<Vec<i64>>, b: Vec<Vec<i64>>) -> Vec<Vec<i64>> {
    let al = a[0].len();
    let bl = b[0].len();
    let tl = al+bl-1;
    let mut ret = dvec!(0; 2, tl);
    for af in 0..2 {
        for bf in 0..2 {
            for i in 0..al {
                for j in 0..bl {
                    let add = a[af][i] * b[bf][j] % MOD;
                    let tf = af^bf;
                    let ti = i+j;
                    ret[af^bf][i+j] += add;
                    if ret[af^bf][i+j] >= MOD {
                        ret[af^bf][i+j] -= MOD;
                    }
                }
            }
        }
    }
    ret
}

const MOD: i64 = 1e9 as i64 + 7;

fn solve(now: usize, par: Option<usize>, graph: &Vec<Vec<usize>>) -> Vec<Vec<i64>> {
    let mut wo = vec![vec![0, 1], vec![0, 0]];
    for &to in &graph[now] {
        if Some(to) == par {
            continue;
        }
        let chi = solve(to, Some(now), graph);
        wo = merge(wo, chi);
    }
    let len = wo[0].len();
    for f in 0..2 {
        let mut mul = 1;
        let mut all = 0;
        for z in 2..len {
            if z % 2 == 1 {
                continue;
            }
            mul *= ((z-1) as i64) % MOD;
            mul %= MOD;
            all += mul * wo[f][z] % MOD;
            all %= MOD;
        }
        wo[f^1][0] += all;
        wo[f^1][0] %= MOD;
    }
    wo
}

fn main() {
    input! {
        n: usize,
        edges: [(usize1, usize1); n-1]
    };
    let mut graph = vec![vec![]; n];
    for (u,v) in edges {
        graph[u].push(v);
        graph[v].push(u);
    }
    let ans = solve(0, None, &graph);
    println!("{}", (MOD+ans[1][0]-ans[0][0])%MOD);
}


Measured memory_bytes: 5372