#include <iostream>

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <queue>

using namespace std;

#define N 100003

struct node

{

    int p,d;

    bool operator <(const node &a)const

    {

        if(p == a.p)

            return d>a.d;

        return p>a.p;

    }

}stone[N];

int maxdis;

priority_queue<node> que;

void GO()

{

    node now,next;

    int OE = ;

    while(!que.empty())

    {

        now = que.top();

        que.pop();

        if(OE)

        {

            next.p = now.p + now.d;

            next.d = now.d;

            que.push(next);

            maxdis = max(next.p,maxdis);

            OE = ;

        }

        else

            OE = ;

    }

}

int main()

{

    int t,i,p,d,n;

    scanf("%d",&t);

    while(t--)

    {

        maxdis = ;

        scanf("%d",&n);

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

        {

            scanf("%d%d",&stone[i].p,&stone[i].d);

            que.push(stone[i]);

        }

        GO();

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

    }

    return ;

}