#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
struct node
{
	int a,b;
}h[N];
bool cmp(node a,node b)
{
	return a.a<b.a;
}
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
		int n;
		cin>>n;
		for(int i=1;i<=n;i++)
		{
			cin>>h[i].a>>h[i].b;
		}
		sort(h+1,h+1+n,cmp);
		int l=0,r=n+1;
		long long suml=0,sumr=0;
		while(l<r)
		{
			r--;
			sumr+=h[r].b;
			while(l+1<r&&suml<sumr)
			{
				l++;
				suml+=h[l].b;
			}
		}
		if(sumr>suml) sumr=suml;
		long long in=0,out=0;
		for(int i=n;i>=1;i--)
		{
			if(sumr>=h[i].b)
			{
				out+=h[i].b*h[i].a;
				sumr-=h[i].b;
			}
			else
			{
				out+=h[i].a*sumr;
				break;
			}
		}
		for(int i=1;i<=n;i++)
		{
			if(suml>=h[i].b)
			{
				in+=h[i].b*h[i].a;
				suml-=h[i].b;
			}
			else
			{
				in+=h[i].a*suml;
				break;
			}
		}
		cout<<out-in<<'\n';
	}
	return 0;
}