#include<bits/stdc++.h>
using namespace std;
long long ksm(long long a,long long b,long long mod){
	long long res=1;
	a%=mod;
	while(b){
		if(b&1) res=res*a%mod;
		a=a*a%mod;
		b>>=1;
	}
	return res;
}

const int N=1e5+10;
int n;
int d[N],mx[N];
vector<int>tr[N];

void dfs(int old,int u){
	for(int v:tr[u]){
		if(v==old) continue;
		d[v]=d[u]+1;
		dfs(u,v);
		mx[u]=max(mx[u],mx[v]);
	}
	mx[u]=max(mx[u],d[u]);
}

bool f=false;
int ans=0;

void dfs1(int old,int u,int up){
	int si=tr[u].size();
	if(si==1){
		ans++;
		if(max(up+1,mx[u]-d[u]+1)<4){
			f=true;
		}
	}
	int x=0,x1=0;
	for(int v:tr[u]){
		if(v==old) continue;
		if(mx[v]>=mx[x]){
			x1=x;x=v;
		}
		else if(mx[v]>mx[x1]){
			x1=v;
		}
	}	

	for(int v:tr[u]){
		if(v==old) continue;
		if(v==x){
			dfs1(u,v,max(up+1,mx[x1]-d[u]+1));
		}
		else{
			dfs1(u,v,max(up+1,mx[x]-d[u]+1));
		}
	}
}

void solve(){
	cin>>n;
	for(int i=1;i<=n;i++){
		tr[i].clear();
		d[i]=mx[i]=0;
	}
	for(int i=1;i<n;i++){
		int x,y;
		cin>>x>>y;
		tr[x].push_back(y);
		tr[y].push_back(x);
	}
	dfs(0,1);
	f=false;
	ans=0;
	dfs1(0,1,0);
	if(f){
		cout<<-1<<'\n';
		return;
	}

	cout<<ans-1<<'\n';
}

int main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int t=1;
	cin>>t;
	while(t--){
		solve();
	}
	return 0;
}