//μ's forever
#include <bits/stdc++.h>
#define N 1000005
//#define getchar nc
using namespace std;
inline char nc(){
    static char buf[100000],*p1=buf,*p2=buf;
    return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;
}
inline int read()
{
    register int x=0,f=1;register char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9')x=(x<<3)+(x<<1)+ch-'0',ch=getchar();
    return x*f;
}
inline void write(register int x)
{
    if(!x)putchar('0');if(x<0)x=-x,putchar('-');
    static int sta[20];register int tot=0;
    while(x)sta[tot++]=x%10,x/=10;
    while(tot)putchar(sta[--tot]+48);
}
int T,n,deg[N];
vector<int> v[N];
int dep[N];
void dfs(int x,int f){
    dep[x]=dep[f]+1;
    for(int i=0;i<(int)v[x].size();++i)
        if(v[x][i]!=f) 
            dfs(v[x][i],x);
}
int main()
{
    T=read();
    while(T--){
        n=read();
        for(int i=1;i<=n;++i) deg[i]=0,v[i].clear();
        for(int i=1;i<n;++i){
            int x=read(),y=read();
            v[x].push_back(y);
            v[y].push_back(x);
            ++deg[x],++deg[y];
        }
        dfs(1,0);
        int pos=0,d=0;
        for(int i=1;i<=n;++i) if(dep[i]>d) d=dep[i],pos=i;
        dfs(pos,0);
        d=0;
        for(int i=1;i<=n;++i) if(dep[i]>d) d=dep[i];
        if(d<=3){
            puts("-1");
        }else{
            int ans=0;
            for(int i=1;i<=n;++i) if(deg[i]==1) ++ans;
            printf("%d\n",ans-1);
        }
    }
    return 0;
}