#include<bits/stdc++.h>
using namespace std;


#define li          long long int
#define rep(i,to)   for(li i=0;i<((li)(to));i++)
#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)
#define pb          push_back
#define sz(v)       ((li)(v).size())
#define bgn(v)      ((v).begin())
#define eend(v)     ((v).end())
#define allof(v)    (v).begin(), (v).end()
#define dodp(v,n)       memset(v,(li)n,sizeof(v))
#define bit(n)      (1ll<<(li)(n))
#define mp(a,b)     make_pair(a,b)
#define rin rep(i,n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1


#define idp if(DBGP)
#define F first
#define S second
#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl
#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl
#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl
#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl
#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl
#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl
#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl
#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl
#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl
#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)
#define p2p(x)      idp p2((x).F, (x).S)
#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}
#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}
#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}
#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}

#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]
#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}

typedef pair<li, li> PI;

// g[i] : i頂点の完全マッチングの場合の数。奇数の場合は0
li g[5050];

// dp[i][j].F : i以下の部分木でiの連結成分頂点数がjで除去変数が偶数なときの場合の数
// dp[i][j].S : i以下の部分木でiの連結成分頂点数がjで除去変数が奇数なときの場合の数
vector<PI> dp[5050];

li n;
vector<li> edge[5050];

inline vector<PI> merge(const vector<PI>& parent, const vector<PI>& child) {
    vector<PI> res(sz(parent) + sz(child) - 1, {0, 0});
    repp(i, 1, sz(parent)) {
        repp(j, 1, sz(child)) {
            // not cut
            res[i + j].F = (res[i + j].F
                            + parent[i].F * child[j].F % MOD
                            + parent[i].S * child[j].S % MOD) % MOD;
            res[i + j].S = (res[i + j].S
                            + parent[i].F * child[j].S % MOD
                            + parent[i].S * child[j].F % MOD) % MOD;
            // cut
            res[i].F = (res[i].F + (parent[i].S * child[j].F % MOD) * g[j] % MOD) % MOD;
            res[i].F = (res[i].F + (parent[i].F * child[j].S % MOD) * g[j] % MOD) % MOD;
            res[i].S = (res[i].S + (parent[i].F * child[j].F % MOD) * g[j] % MOD) % MOD;
            res[i].S = (res[i].S + (parent[i].S * child[j].S % MOD) * g[j] % MOD) % MOD;
        }
    }
    return res;
}

inline void calc(li now, li from) {
    vector<vector<PI>> dpp(1);
    dpp[0].pb({0, 0});
    dpp[0].pb({1, 0});
    for (auto child : edge[now]) {
        if (child == from) {
            continue;
        }
        calc(child, now);
        dpp.pb(merge(dpp.back(), dp[child]));
    }
    dp[now] = dpp.back();

    //p2(now, from);
    //dumpi2(dp[now]);
}

int main() {
    g[2] = 1;
    rep(i, 5050) {
        if (i > 2) {
            g[i] = (g[i - 2] * (i - 1)) % MOD;
        }
    }
    rin{
        dp[i].resize(2);
    }

    cin >> n;
    rep(i, n - 1) {
        li a, b;
        cin >> a >> b;
        a--;
        b--;
        edge[a].pb(b);
        edge[b].pb(a);
    }
    calc(0, -1);

    li res = 0;
    rep(i, sz(dp[0])) {
        //p4("+++", dp[0][i].F, g[i], res);
        res = (res + dp[0][i].F * g[i] % MOD) % MOD;
    }
    rep(i, sz(dp[0])) {
        //p4("---", dp[0][i].S, g[i], res);
        res = (res + (MOD - dp[0][i].S * g[i] % MOD)) % MOD;
    }
    cout << res << endl;

    return 0;
}

Measured memory_bytes: 196608