#include <bits/stdc++.h>

using namespace std;

using ll = long long;

void solve(){
    int n;
    cin >> n;
    vector<pair<int,int>> a(n);

    for (auto &[v,w] : a){
        cin >> v >> w;
    }

    auto calc = [&](int x)->bool{
        vector<int> s,b;
        for (auto [v,w] : a){
            if (v < x) s.push_back(w);
            else
                b.push_back(w + v - x);
        }
        sort(s.begin(),s.end());
        sort(b.begin(),b.end());
        int i,j;
        for (i = 0,j = 0;i < s.size() && j < b.size();){
            while (j < b.size() && s[i] > b[j])
                j++;
            if (j < b.size() && s[i] <= b[j]) i++;
        }
        if (i == s.size()) return true;
        return false;
    };

    int l = 0 ,r = 1e9 + 7;
    while (l + 1 < r){
        int mid = l + r >> 1;
        if (calc(mid)) l = mid;
        else
            r = mid;
    }

    cout << l << "\n";
}

int main(){
	ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t;
    cin >> t;

    while (t--){
        solve();
    }

	return 0;
}