#include<iostream>
#include<fstream>

using namespace std;

int main()
{
	ifstream f("linterv.in");
	ofstream g("linterv.out");
	int n, is, id, ls, ld, i, suma=0, t, j;
	
	f>>t;
	while(t!=0)
	{
		suma=0;
		f>>n;
		f>>is>>id; 
		ls=is;
		ld=id;
		for(i=1;i<n;i++)
		{
			if(is<ls || id>ld)
			{
				if(is<ls)
					ls=is;
				if(id>ld)
					ld=id;
			}
			else
			{
				if(is>ls && id<ld)
					break;
				else
					for(j=ls;j<=ld;j++)
						suma++;
			}
			f>>is>>id;
		}
		g<<suma<<'\n';
		t--;
	}
	f.close();
	g.close();
	return 0;
}