#include <iostream>
using namespace std;
 
int main() {
	int t;
	cin>>t;
	while(t--)
	{
	    int a,b,n,x,s;
	    cin>>n>>x>>s;
	    if(n>100000||s>10000||n<2||s<1||x>n||x<1)
	    {
	    	cout<<-1<<"wrong constrainst check"<<endl;
	    	return -1;
	    }
	    while(s--)
	    {
	        cin>>a>>b;
	        if(a==b||a>n||b>n||a<1||b<1)
	        {
	        	cout<<-1<<"wrong constrainst check"<<endl;
	        	return -1;
	        }
	        if(x==a)
	        {
	            x=b;
	        }
	        else if(x==b)
	        {
	            x=a;
	        }
	    }
	    cout<<x<<endl;
	}
	return 0;
}