#include <bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
const int N = 1000010;
typedef pair<int, int> PII;
struct node
{
    int v, w;
} a[N];
int n;
bool cmp(node x, node y)
{
    return x.v > y.v;
}
bool check(int mid)
{
    priority_queue<int> o;
    priority_queue<int> p;
    for (int i = 1; i <= n; i++)
    {
        if (a[i].v >= mid)
        {
            o.push(a[i].v + a[i].w - mid);
            // cout << o.top() << endl;
        }
        else
            p.push(a[i].w);
    }
    if (o.size() <= 0)
    {
        return false;
    }
    while (p.size())
    {
        if (o.top() >= p.top())
        {
            o.pop();
            p.pop();
        }
        else
            return false;
    }
    return true;
}
void solve()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i].v >> a[i].w;
    }
    int l = 0, r = 1e9 + 10;
    // sort(a + 1, a + 1 + n, cmp);
    while (l < r)
    {
        int mid = (l + r + 1) / 2;
        if (check(mid))
        {
            l = mid;
        }
        else
            r = mid - 1;
        // cout << l << " " << r << endl;
    }
    cout << l << endl;
}
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    cin >> T;
    while (T--)
    {
        solve();
    }
    return 0;
}