#include <bits/stdc++.h>
#define int long long
#define inf 0x3f3f3f3f
#define ll long long
#define pii pair<int, int>
#define tii tuple<int, int, int>
#define db double
#define all(a) a.begin(), a.end()
using namespace std;
const int maxn = 1e5 + 10;
const int mod = 998244353;
pii arr[maxn];
int n;
bool ck(int mid) {
    vector<int> vec1, vec2;
    for (int i = 1; i <= n; i++) {
        auto [v, w] = arr[i];
        if (mid < v) {
            vec1.push_back(w + (v - mid));
        } 
        else if (mid > v) 
            vec2.push_back(w);
    }
    sort(all(vec1)), sort(all(vec2));
    if (vec2.size() > vec1.size()) return 0;
    reverse(all(vec1)), reverse(all(vec2));
    for (int i = 0; i < vec2.size(); i++)
        if (vec1[i] < vec2[i]) return 0;
    return 1;
}
void solve() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        int v, w; cin >> v >> w;
        arr[i] = {v, w};
    }
    sort(arr + 1, arr + 1 + n);
    int l = 1, r = 1e9, ans = 1;
    while (l <= r) {
        int mid = (l + r) >> 1;
        if (ck(mid)) ans = mid, l = mid + 1;
        else r = mid - 1;
    }
    cout << ans << "\n";
}
signed main() {
    // freopen("1.in", "r", stdin);
    // freopen("1.out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int t = 1;
    cin >> t;
    while (t--)
        solve();
    return 0;
}