A

#include <bits/stdc++.h>

using namespace std;

#define _test   int _TEST; cin>>_TEST; while(_TEST--)
#define ff     first
#define ss     second

int main()
{
    _test
    {
        int ans = -1;

        int n;
        cin>>n;

        vector<pair<int, int>> se(n);
        for(auto &[s, e]: se)       cin>>s>>e;

        int f = 1;
        int mmax = 0;

        for(int i=1; i<n; i++)
        {
            if(se[i].ff >= se[0].ff)
                mmax = max(mmax, se[i].ss);
        }

        if(se[0].ss > mmax)     cout<<se[0].ff<<"\n";
        else                    cout<<-1<<"\n";
    }
}