#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5;

vector<int> G[N];
map<int, int> M;

void dfs(int x, int fa = 0)
{
    if (G[x].size() == 1) {
        ++M[fa];
    }
    for (auto v : G[x]) {
        if (v != fa) {
            dfs(v, x);
        }
    }
    return;
}

signed main()
{
    int T;
    scanf("%d", &T);
    while (T--) {
        int n;
        scanf("%d", &n);
        M.clear();
        for (int i = 1; i <= n; ++i) {
            G[i].clear();
        }
        for (int i = 1, x, y; i < n; ++i) {
            scanf("%d%d", &x, &y);
            G[x].push_back(y);
            G[y].push_back(x);
        }
        if (n <= 3) {
            puts("-1");
            continue;
        }
        int rt = 0;
        for (int i = 1; i <= n; ++i) {
            if (G[i].size() != 1) {
                rt = i;
            }
        }
        dfs(rt);
        if (M.size() == 1) {
            puts("-1");
            continue;
        }
        vector<int> tp;
        for (auto [x, y] : M) {
            tp.push_back(y);
        }
        printf("%d\n", max(accumulate(tp.begin(), tp.end(), 0) >> 1, *max_element(tp.begin(), tp.end())));
    }
    return 0;
}