//21
#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;

const int maxn = 5001;
const int lbt = 1e9 + 7;

int n;
int xs[maxn];
vector<int> adj[maxn];
int prt[maxn];
int cnt[maxn];
int dp[maxn][maxn];

void dfs(int u);

int main() {
	scanf("%d", &n);
	xs[0] = 1;
	for (int i = 2; i <= n; i++) {
		xs[i] = (long long)(i - 1) * xs[i - 2] % lbt;
	}
	for (int i = 1; i < n; i++) {
		int u, v;
		scanf("%d%d", &u, &v);
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	dfs(1);
	int ans = (lbt - dp[1][0]) % lbt;
	printf("%d", ans);
	return 0;
}

void dfs(int u) {
	static int tmp[maxn];
	dp[u][0] = 1;
	for (int i = 0; i < adj[u].size(); i++) {
		int v = adj[u][i];
		if (v == prt[u]) continue;
		prt[v] = u;
		dfs(v);
		for (int i = 0; i <= cnt[u] + cnt[v]; i++) {
			tmp[i] = 0;
		}
		for (int i = 0; i <= cnt[u]; i++) {
			for (int j = 0; j <= cnt[v]; j++) {
				tmp[i + j] = (tmp[i + j] + (long long)dp[u][i] * dp[v][j]) % lbt;
			}
		}
		for (int i = 0; i <= cnt[u] + cnt[v]; i++) {
			dp[u][i] = tmp[i];
		}
		cnt[u] += cnt[v];
	}
	for (int i = cnt[u]; i >= 0; i--) {
		dp[u][i + 1] = dp[u][i];
	}
	cnt[u]++;
	dp[u][0] = 0;
	for (int i = 1; i <= cnt[u]; i++) {
		if (i % 2 == 0) dp[u][0] = (dp[u][0] + (long long)(lbt - xs[i]) * dp[u][i]) % lbt;
	}
}