#include<bits/stdc++.h>
using namespace std;
#define int long long
int const maxn = 1e5+10;;
struct node{
	int a,b;
}p[maxn];
bool cmp(node y,node x){
	return y.a < x.a;
}

signed main(){
	int t;
	cin >> t ;
	while(t--){
		int n;
		cin >> n ;
		int sum = 0;
		for(int i = 1;i <= n;i ++){
			cin >> p[i].a >> p[i].b;
			sum += p[i].b;
		}
		int ans = 0;
		sort(p+1,p+n+1,cmp);
		int k = sum/2;
		for(int i = 1;i <= n;i ++){
			if(k==0){
				ans += p[i].a*p[i].b;
			}else {
				if(p[i].b <= k){
				ans -= p[i].a*p[i].b;
				k-=p[i].b;
			}else {
				if(sum%2){
					ans += p[i].a*(p[i].b -k - 1);
				}else {
					ans += p[i].a*(p[i].b-k);
				}
				
				ans-= p[i].a*k;
				k = 0;
			}
			}
			
			
		}
		cout << ans<<'\n';
		
		
	}
	return 0;
}