#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1e5 + 10;
int n;
struct node
{
	int v;
	int w;
}xiaoyu[N];
struct nodes
{
	int v;
	int w;
}xjh[N];
bool cmp1(node x, node y)
{
	return x.v + x.w > y.v + y.w;
}
bool cmp2(nodes x, nodes y)
{
	return x.w > y.w;
}
bool check(int x)
{
	vector<int>a;
	vector<int>b;
	//找速度比较大的
	for (int i = 1; i <= n; i++)
	{
		if (xiaoyu[i].v > x) a.push_back(xiaoyu[i].v + xiaoyu[i].w - x);//根据v+w排序，所以体重也是排序
	}
	//找速度比较小的
	for (int i = 1; i <= n; i++)
	{
		if (xjh[i].v < x) b.push_back(xjh[i].w);
	}
	//左面数量少    速度太大
	if (a.size() < b.size()) return false;
	else
	{
		int len = b.size();
		for (int i = 0; i < len; i++)
		{
			if (a[i] < b[i]) return false;//不够背
		}
	}
	return true;
}
void solve()
{
	cin >> n;
	int l = 1e9 + 10;
	int r = -1;
	for (int i = 1; i <= n; i++)
	{
		int v, w;
		cin >> v >> w;
		l = min(l, v);
		r = max(r, v);
		xiaoyu[i].v = v;
		xiaoyu[i].w = w;
		xjh[i].v = v;
		xjh[i].w = w;
	}
	sort(xiaoyu + 1, xiaoyu + 1 + n, cmp1);
	sort(xjh + 1, xjh + 1 + n, cmp2);
	while (l < r)
	{
		int mid = (l + r+1) >> 1;
		if (check(mid))l = mid;
		else r = mid -1;
	}
	cout << l << endl;
}
signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t;
	t = 1;
	cin >> t;
	while (t--)
	{
		solve();
	}
	return 0;
}