#include <iostream>
#include <cstring>
#include <algorithm>
#include <set>
#include <map>

using namespace std;
const int N = 2e5 + 10, M = 2 * N, INF = 0x3f3f3f3f;
const int mod = 998244353;
int n, m, a[N];
int h[N], e[M], ne[M], w[M], idx;
int depth[N], sz[N], son[N], d[N];
int ans = 1;

void add(int a, int b) {
    e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}

void dfs(int u, int fa) {
    depth[u] = depth[fa] + 1;
    for(int i = h[u]; ~i ; i = ne[i]) {
        int j = e[i];
        if(j == fa) continue;
        dfs(j, u);
    }
}

signed main () {
    int T = 1;
    cin >> T;
    while (T-- ) {
        cin >> n;
        for (int i = 1; i <= n; i++ )
            h[i] = -1, d[i] = 0;
        idx = 0;
        for(int i = 1; i < n ; i ++ ) {
            int a, b;
            cin >> a >> b;
            add(a, b), add(b, a);
            d[a]++, d[b]++ ;
        }
        int ans = 0;
        for (int i = 1; i <= n; i++ ) 
            if (d[i] == 1) ans++ ;
        dfs(1, 0);
        int root = 1;
        for (int i = 1; i <= n; i++ )
            if (depth[root] < depth[i]) root = i;
        dfs(root, 0);
        int mx = 0;
        for (int i = 1; i <= n; i++ ) 
            mx = max(mx, depth[i]);
        if (mx <= 3) cout << -1 << endl;
        else cout << (ans + 1) / 2 << endl;
    }
}