#include <bits/stdc++.h>
#define int long long
#define endl "\n"
using namespace std;
const int mod = 1e9 + 7;
struct node
{
    int v;
    int cnt;
} s[1000005];
bool cmp(node A, node B)
{
    return A.v < B.v;
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    int T;
    cin >> T;
    while (T--)
    {
        int n;
        cin >> n;
        int flag = 0;
        for (int i = 1; i <= n; i++)
        {
            cin >> s[i].v >> s[i].cnt;
            flag += s[i].cnt;
        }
        flag = flag / 2;
        sort(s + 1, s + n + 1, cmp);
        int Buy = 0;
        int Sale = 0;
        int sum = 0;
        for (int i = 1; i <= n; i++)
        {
            if (sum <= flag && (sum + s[i].cnt) <= flag)
            {
                Buy += (s[i].cnt * s[i].v);
                sum += s[i].cnt;
            }
            else
            {
                Buy += s[i].v * (flag - sum);
                break;
            }
        }
        sum = 0;
        for (int i = n; i >= 1; i--)
        {
            if (sum <= flag && (sum + s[i].cnt) <= flag)
            {
                Sale += (s[i].cnt * s[i].v);
                sum += s[i].cnt;
            }
            else
            {
                Sale += s[i].v * (flag - sum);
                break;
            }
        }
        cout << (Sale - Buy) << endl;
    }

    return 0;

} /*Orz Orz Orz ACACAC*/