y2k

/*
    Task    :
    Author  : Phumipat C. [MAGCARI]
    Language: C++
    Created : 03 May 2023 [18:53]
*/
#include<bits/stdc++.h>
using namespace std;
void solve(){
    int n,ans = 0;
    cin >> n;
    priority_queue<int > heap;
    for(int i=1;i<=n;i++){
        int y,k;
        cin >> y >> k;
        ans+=y;
        heap.push(-(k-y));
    }
    for(int i=1;i<=n/2;i++){
        ans-=heap.top();
        heap.pop();
    }
    cout << ans << '\n';
}
int main(){
    int q;
    cin >> q;
    while(q--){
        solve();
    }
    return 0;
}