#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

template<int MOD>
class ModInt {
public:
    ModInt() :value(0) {}
    ModInt(long long val) :value((int)(val<0 ? MOD + val % MOD : val % MOD)) { }

    ModInt& operator+=(ModInt that) {
        value = value + that.value;
        if (value >= MOD)value -= MOD;
        return *this;
    }
    ModInt& operator-=(ModInt that) {
        value -= that.value;
        if (value<0)value += MOD;
        return *this;
    }
    ModInt& operator*=(ModInt that) {
        value = (int)((long long)value * that.value % 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 pow(long long k) const {
        ModInt n = *this, res = 1;
        while (k) {
            if (k & 1)res *= n;
            n *= n;
            k >>= 1;
        }
        return res;
    }
    ModInt inverse() const {
        long long a = value, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        return ModInt(u);
    }
    int toi() const { return value; }

private:
    int value;
};
typedef ModInt<1000000007> mint;
ostream& operator<<(ostream& os, const mint& x) {
    os << x.toi();
    return os;
}

const int MAX_N = 5003;
int N;
vi G[MAX_N];
vector<mint> dp[MAX_N][2], ne[MAX_N][2];
mint ways[MAX_N];

void f(int u, int p) {
    rep(i, 2)dp[u][i].resize(2);
    dp[u][0][1] = 1;

    each(v, G[u]) {
        if (v == p) {
            continue;
        }

        f(v, u);

        int n = sz(dp[u][0]);
        int m = sz(dp[v][0]);

        rep(i, 2)ne[u][i].assign(n + m - 1, 0);

        rep(i, n)rep(j, m) {
            rep(a, 2)rep(b, 2) {
                // 繋ぐ場合
                ne[u][(a + b) & 1][i + j] += dp[u][a][i] * dp[v][b][j];
                // 繋がない場合
                ne[u][(a + b + 1) & 1][i] += dp[u][a][i] * dp[v][b][j] * ways[j];
            }
        }

        rep(i, 2)swap(ne[u][i], dp[u][i]);
    }
}


void solve() {
    cin >> N;
    rep(i, N - 1) {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        G[u].push_back(v);
        G[v].push_back(u);
    }

    ways[0] = 1;
    for (int i = 2; i <= N; i += 2) {
        ways[i] = ways[i - 2] * (i - 1);
    }

    f(0, -1);

    mint re = 0;
    rep(i, N + 1) {
        re += dp[0][0][i] * ways[i];
        re -= dp[0][1][i] * ways[i];
    }
    cout << re << endl;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}

Measured memory_bytes: 70400