#include <bits/stdc++.h>
using namespace std;
int main()
{
	int n,i,t,b,x,y,o;
	cin>>t;
	while(t--)
	{
		b=0;
		o=1;
		cin>>n;
		for(i=0;i<n;++i)
		{
			cin>>x>>y;
			if(x>b)
			{
				cout<<0<<endl;
				o=0;
				break;
			}
			b+=y;
			b-=x;
		}
		if(o==1)cout<<n+1<<endl;
	}
	return 0;
}

求调.....