#include <iostream>
#include <algorithm>
#include <string>
#include <set>
#include <vector>
#include <assert.h>
using namespace std;



long long readInt(long long l,long long r,char endd){
	long long x=0;
	int cnt=0;
	int fi=-1;
	bool is_neg=false;
	while(true){
		char g=getchar();
		if(g=='-'){
			assert(fi==-1);
			is_neg=true;
			continue;
		}
		if('0'<=g && g<='9'){
			x*=10;
			x+=g-'0';
			if(cnt==0){
				fi=g-'0';
			}
			cnt++;
			assert(fi!=0 || cnt==1);
			assert(fi!=0 || is_neg==false);
			
			assert(!(cnt>19 || ( cnt==19 && fi>1) ));
		} else if(g==endd){
			assert(cnt>0);
			if(is_neg){
				x= -x;
			}
			assert(l<=x && x<=r);
			return x;
		} else {
			assert(false);
		}
	}
}
string readString(int l,int r,char endd){
	string ret="";
	int cnt=0;
	while(true){
		char g=getchar();
		assert(g!=-1);
		if(g==endd){
			break;
		}
		cnt++;
		ret+=g;
	}
	assert(l<=cnt && cnt<=r);
	return ret;
}
long long readIntSp(long long l,long long r){
	return readInt(l,r,' ');
}
long long readIntLn(long long l,long long r){
	return readInt(l,r,'\n');
}
string readStringLn(int l,int r){
	return readString(l,r,'\n');
}
string readStringSp(int l,int r){
	return readString(l,r,' ');
}


int T;
int n,sm_n=0;
int L[200200];
int R[200200];
int rng[200200][2];
set<int> g;
int mx_l,sol=0;

bool dfs(int nd){
	if(L[nd] == -1)return true;
	if(!dfs(L[nd]))return false;
	if(!dfs(R[nd]))return false;
	if(rng[L[nd]][1] + 1 == rng[R[nd]][0]){
		rng[nd][0] = rng[L[nd]][0];
		rng[nd][1] = rng[R[nd]][1];
	} else if(rng[R[nd]][1] + 1 == rng[L[nd]][0]) {
		sol++;
		rng[nd][0] = rng[R[nd]][0];
		rng[nd][1] = rng[L[nd]][1];
	} else {
		return false;
	}
	return true;
}
int main(){
	T=readIntLn(1,1000);
	while(T--){
		mx_l=0;
		g.clear();
		n=readIntLn(2,200000);
		sm_n += n;
		sol=0;
		assert(sm_n<=200000);
		for(int i=1;i<=n;i++){
			int a,b;
			a=readIntSp(-1,n);
			b=readIntLn(1,n);
			if(a == -1){
				mx_l=max(mx_l,b);
				assert(!g.count(b));
				g.insert(b);
				L[i] = R[i]  = -1;
				rng[i][0] = rng[i][1] = b;
			} else {
				assert(a != 0);
				L[i]=a;
				R[i]=b;
			}
		}
		assert(g.size() == mx_l);
		if(dfs(1)){
			cout<<sol<<endl;
		} else {
			cout<<-1<<endl;
		}
	}
	assert(getchar()==-1);
}