#include <iostream>
#include <vector>
using namespace std;
int zero=0,unu=0;
vector<int>adj[200005];
void dfs(int curr,int par,int val)
{
    if(val==0)
    {
        zero++;
    }
    else
    {
        unu++;
    }
    for(auto k:adj[curr])
    {
        if(k!=par)
        {
            dfs(k,curr,1^val);
        }
    }
}
int main()
{
    int n,i,j,k,l,op,t,a,b;
    cin>>t;
    for(op=1;op<=t;op++)
    {
        cin>>n;
        zero=0;
        unu=0;
        int leaf=0;
        for(i=1;i<n;i++)
        {
            cin>>a>>b;
            adj[a].push_back(b);
            adj[b].push_back(a);
        }
        dfs(1,0,0);
        for(i=1;i<=n;i++)
        {
            if(adj[i].size()==1)
            {
                leaf++;
            }
        }
        if(zero>=2 && unu>=2)
        {
            cout<<leaf-1;
        }
        else
        {
            cout<<-1;
        }
        cout<<'\n';
        for(i=1;i<=n;i++)
        {
            adj[i].clear();
        }
    }
    return 0;
}