#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);
    }

    vector<array<int, 2>> d0(n + 1), d1(n + 1);
    vector<int> ans(n + 1);

    auto dfs0 = [&](auto && self, int u, int fa) -> void {
        for (auto & v : adj[u]) {
            if (v == fa) continue;
            self(self, v, u);
            if (d0[v][0] >= d0[u][0]) {
                d1[u] = d0[u];
                d0[u] = {d0[v][0] + 1, v};
            } else if (d0[v][0] >= d1[u][0]) {
                d1[u] = {d0[v][0] + 1, v};
            }
        }
    };

    dfs0(dfs0, 1, 0);

    auto dfs = [&](auto && self, int u, int fa, int md) -> void {
        ans[u] = max(d0[u][0], md);

        if(adj[u].size() == 1) {
            if (cnt != -1) {
                cnt++;
                if (ans[u] <= 2) {
                    cnt = -1;
                }
            }
        }

        for (auto &v : adj[u]) {
            if (v == fa) continue;
            self(self, v, u, (v == d0[u][1] ? max(md, d1[u][0]) : max(md, d0[u][0])) + 1);
        }
    };

    dfs(dfs, 1, 0, 0);

    if (cnt == -1) {
        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;
}