#include<bits/stdc++.h>
using namespace std;

int main()
{
    int T;
    cin >> T;
    while(T --)
    {
        int n;
        scanf("%d", &n);

        int xx = 0, yy = 0;
        for(int i = 0; i < n; i ++)
        {
            int x, y;
            scanf("%d%d", &x, &y);
            xx = max(xx, x);
            yy = max(yy, y);
        }

        cout << xx + yy << endl;
    }

    return 0;
}