#include <bits/stdc++.h>
using namespace std;

void solve() {
    int n;
    cin >> n;
    vector<array<int, 2>>a(n + 1);
    int cnt = 0;
    for (int i = 1;i <= n;i++) {
        cin >> a[i][0] >> a[i][1];
        cnt += a[i][1];
    }
    sort(a.begin() + 1, a.end());
    // for (int i = 1;i <= n;i++) {
        // cout << a[i][0] << " " << a[i][1] << "\n";
    // }
    int x = cnt / 2;
    int s = 0;
    for (int i = 1;i <= n;i++) {
        int t = min(x, a[i][1]);
        // cout << t << "\n";
        s -= t * a[i][0];
        a[i][1] -= t;
        x -= t;
    }

    x = cnt / 2;
    for (int i = n;i >= 1;i--) {
        int t = min(x, a[i][1]);
        s += t * a[i][0];
        a[i][1] -= t;
        x -= t;
    }
    cout << s << "\n";

}

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int T = 1;
#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif
    cin >> T;
    while (T--)
        solve();
    return 0;
}