#include<bits/stdc++.h>
#define ll long long
#define all(x) x.begin(), x.end()
#define lowbit(i) ((i)&(-i))
#define pii pair<int,int>
#define endl '\n'
#define mk(x,y) make_pair(x,y)
#define popcount(x) __builtin_popcount(x)
#define LF(x) fixed<<setprecision(x)
const double pi=3.14159265358979323846;
const double eps=1e-9;
const int inf=1e9;
const long long INF=4e18;
const int mod=1e9+7;
using namespace std;
const int N=1e5+10;
struct ed
{
	ll a,b;
	bool operator<(const ed& t)const{
		return a<t.a;
	}
};
void solve()
{
    int n;
    cin>>n;
    vector<ed>x(n+1);
    for(int i=1;i<=n;i++){
    	cin>>x[i].a>>x[i].b;
    }
    sort(x.begin()+1,x.end());
    // vector<vector<int>>dp(n+1);
    ll ans=0;
    ll sum=0;
    for(int i=1,j=n;i<j;i++){
    	ll ans1=ans;
    	// cout<<i<<" "<<j<<endl;
    	ans1-=x[i].a*x[i].b;
    	sum+=x[i].b;
    	// cout<<ans<<" "<<sum<<" "<<x[j].b<<" ";
    	if(x[j].b>sum){
    		ans1+=x[j].a*sum;
    		sum=0;
    		x[j].b-=sum;
    	}
    	else{
    		ans1+=x[j].a*x[j].b;
    		sum-=x[j].b;
    		j--;
    	}
    	// cout<<ans1<<endl;
    	ans=max(ans,ans1);
    }
    cout<<ans<<endl;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    
    int T=1;
    cin>>T;
    while(T--){
        solve();
    }
    return 0;
}