#include<bits/stdc++.h>
using namespace std;
const int INF=0x3f3f3f3f;
#define endl '\n'
#define x first
#define y second
typedef long long ll;
typedef pair<int,int> PII;
PII a[100010];
int n,cnt=0;
void solve()
{
	
	
	scanf("%d",&n);
	for(int i=1;i<=n;i++) 
	{
		scanf("%d%d",&a[i].x,&a[i].y);	
		cnt+=a[i].y;
	}
	sort(a+1,a+n+1);
	
	int l=1,r=n;
	ll ans=0;
	while(l<r)
	{
		int res=min(a[l].y,a[r].y);
		a[l].y-=res;
		a[r].y-=res;
		ans+=(a[r].x-a[l].x)*res;
		if(a[l].y==0)l++;
		else r--;
	}
	
	printf("%lld\n",ans);
	//cout<<xs-cb<<endl;
}
/*
10 2
20 4
25 
30 7
50 1
*/
int main()
{
	//ios::sync_with_stdio(false);
	//ios::sync_with_stdio(0);cin.tie(0),cout.tie(0);
	int t;
	scanf("%d",&t);
	while(t--)
	{
		solve();
	}
	return 0;
}