#include <bits/stdc++.h>
#define endl '\n'
#define int long long
#define x first
#define y second
using namespace std;
typedef pair<int, int> PII;

void solve() {
    int n;
    cin >> n;
    vector<PII> v(n);
    int cnt = 0, tot = 0;
    for (auto &[a, b] : v) {
        cin >> a >> b;
        cnt += b;
        tot += a * b;
    }
    sort(v.begin(), v.end());
    int cnt1 = 0, tot1 = 0, flg;
    for (int i = 0; i < (int)v.size(); i++) {
        auto [a, b] = v[i];
        if ( cnt1 + b < cnt / 2 ) {
            cnt1 += b;
            tot1 += a * b;
        } else {
            if ( cnt1 + b < cnt / 2 ) {
                flg = a;
            } else {
                flg = v[i + 1].x;
            }
            tot1 += a * ( cnt / 2 - cnt1 );
            cnt1 = cnt / 2;
            break;
        }
    }
    if ( cnt % 2 == 0 ) flg = 0;
    cout << tot - 2 *  tot1 - flg << endl;
}

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