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

void QAQ() {
    int n, cnt = 0;
    cin >> n;

    vector adj(n + 1, vector<int>());

    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].emplace_back(v), adj[v].emplace_back(u);
    }

    for (int i = 1; i <= n; i++) {
        cnt += adj[i].size() == 1;
    }

    vector<int> d(n + 1);
    int c = 0;

    auto dfs = [&](auto && self, int u, int fa) -> void {
        for (auto & v : adj[u]) {
            if (v == fa) continue;
            d[v] = d[u] + 1;
            if (d[v] > d[c]) c = v;
            self(self, v, u);
        }
    };

    dfs(dfs, 1, 0);

    d[c] = 0;
    dfs(dfs, c, 0);

    if(d[c] <= 2) {
        cout << "-1\n";
    } else {
        cout << cnt - 1 << "\n";
    }
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int t = 1;
    cin >> t;

    while (t--) {
        QAQ();
    }
    return 0;
}