#include <bits/stdc++.h>
#define int long long
#define all(x) x.begin(), x.end()
#define lowbit(i) ((i)&(-i))
#define pii pair<int,int>
#define endl '\n'
#define mk(x,y) make_pair(x,y)
#define popcount(x) __builtin_popcount(x)
#define LF(x) fixed<<setprecision(x)
const double pi = 3.14159265358979323846;
const double eps = 1e-9;
const int inf = 1e9;
const long long INF = 4e18;
const int mod = 1e9+7;
using namespace std;
const int N = 1e5+10;

void solve() {
    int n;
    cin >> n;
    vector<int> a(n + 1), b(n + 1), id(n + 1);
    for(int i = 1; i <= n; i++) {
    	cin >> a[i] >> b[i];
    	id[i] = i;
    }
    sort(id.begin() + 1, id.end(), [&](int i, int j){
    	if(a[i] + b[i] == a[j] + b[j])return b[i] > b[j];
    	return a[i] + b[i] > a[j] + b[j];
    });
    // // for(int i = 1; i <= n; i++) {
    // // 	cout << a[id[i]] << " \n"[i == n];
    // // }
    int l = 1, r = inf;
    auto check = [&](int x) {
    	vector<array<int,2>>pos;
    	vector<array<int,2>>g;
    	for(int i = 1; i <= n; i++) {
    		if(a[id[i]] < x) {
    			pos.push_back({a[id[i]], b[id[i]]});
    		}
    		else g.push_back({a[id[i]], b[id[i]]});
    	}
    	if(pos.size() == 0)return true;
    	if(pos.size() > g.size())return false;
    	vector<int> vis(n + 1);
    	for(auto[v, w]: pos) {
    		bool flag = 1;
    		for(int i = 0; i < g.size(); i++) {
    			if(vis[i])continue;
    			int v_ = g[i][0];
    			int w_ = g[i][1];
    			if(w_ >= w) {
    				vis[i] = 1;
    				flag = false;
    				break;
    			}
    			else {
    				if(v_ - (w - w_) >= x) {
    					vis[i] = 1;
    					flag = false;
    					break;
    				}
    			}
    		}
    		if(flag)return false;
    	}
    	return true;
    };
    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(false);
    cin.tie(0);
    cout.tie(0);
    
    int T = 1;
    cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}