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

#define U(x) ((int)x.size())
#define pb push_back
const int N=1e5+100;
#define gc getchar()
#define rd read()
inline int read(){
	int x=0,f=0; char c=gc;
	for(;c<'0'||c>'9';c=gc) f|=(c=='-');
	for(;c>='0'&&c<='9';c=gc) x=(x<<1)+(x<<3)+(c^48);
	return f?-x:x;
}

int n,m=0,tot=0,a[N];
vector<int> G[N];
inline int is(int x){ return U(G[x])==1; }

void solve(){
	n=rd,m=tot=0; for(int i=1,x,y;i<n;++i) x=rd,y=rd,G[x].pb(y),G[y].pb(x);
	
	for(int i=1;i<=n;++i) if((!is(i))&&((a[++m]=0)==0)) for(int v:G[i]) a[m]+=is(v);
	sort(a+1,a+m+1);
	for(int i=1;i<=m;++i) tot+=a[i];
	if(a[m]==tot) printf("-1\n");
	else{
		for(int i=1;i<=m;++i) a[i]-=a[i-1];	
		printf("%d\n", (tot-a[m])/2+a[m]);
	}
	for(int i=1;i<=n;++i) G[i]={};
}

int main(){
	
	int T=rd;
	while(T--) solve();
	
	return 0;
}
/*
1
5
1 2
2 3
3 4
3 5
*/