#include<iostream>

#include<cstdio>

#include<cstring>

#include<queue>

using namespace std;

#define maxn 100010

struct Node

{

    int x,y,id;

    friend bool operator < (Node a,Node b)

    {

        if(a.x != b.x) return a.x > b.x;

        else if(a.y != b.y) return a.y > b.y;

        else return a.id < b.id;

    }

} node[maxn];

priority_queue<Node>que;

int main()

{

    int t,n;

    scanf("%d",&t);

    while(t--)

    {

        scanf("%d",&n);

        for(int i = ; i < n; i++)

        {

            scanf("%d%d",&node[i].x,&node[i].y);

            node[i].id = i+;

            que.push(node[i]);

        }

        int tot = ,maxt = -;

        while(!que.empty())

        {

            tot++;

            Node tmp = que.top();

            que.pop();

            if(tot &  == )

            {

                Node next = tmp;

                next.x = tmp.x + tmp.y;

                if(next.x > maxt) maxt = next.x;

                que.push(next);

            }

        }

        printf("%d\n",maxt);

    }

    return ;

}