#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e5 + 5;

int N, v[maxn], w[maxn];
vector<int> good;
vector<int> bad;

bool check(int mid) {
  good.clear(), bad.clear();
  for (int i = 1; i <= N; i++) {
    if (v[i] < mid) bad.push_back(w[i]);
    if (v[i] > mid) good.push_back(w[i] + v[i] - mid);
  }
  sort(good.begin(), good.end());
  reverse(good.begin(), good.end());
  sort(bad.begin(), bad.end());
  reverse(bad.begin(), bad.end());
  if (bad.size() > good.size()) return false;
  int pos = 0;
  for (int i = 0; i < (int)bad.size(); i++) {
    while (pos + 1 < (int)good.size() && good[pos + 1] >= bad[i]) pos++;
    if (pos < i || good[pos] < bad[i]) return false;
  }
  return true;
}

void solve() {
  cin >> N;
  for (int i = 1; i <= N; i++) cin >> v[i] >> w[i];
  int L = 0, R = 1000000000, res = 0;
  while(L <= R) {
    int mid = (L + R) >> 1;
    if (!check(mid)) R = mid - 1;
    else res = mid, L = mid + 1;
  }
  printf("%d\n", res);
}

int main() {
  //  freopen("a.in", "r", stdin);
  int T = 0;
  cin >> T;
  while(T--) solve();
  return 0;
}