#include<iostream>
#include<cstring>
#include<algorithm>

using namespace std;
int res,cnt;
const int N=1e5+5;

struct Node{
    int y,x;
    bool operator<(const Node &m)const{
        return x+y<m.x+m.y;
    }
}node[N];


int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        int n;scanf("%d",&n);
        res=0,cnt=0;
        for(int i=1,x,y;i<=n;i++){
            scanf("%d%d",&x,&y);
            node[i]={x,y};
        }
        sort(node+1,node+1+n);
        int temy=node[n].y;
        int temx=node[n].x;
        
        int tem2x=node[n-1].x;
        int tem2y=node[n-1].y;
        if(temx+temy==tem2x+tem2y)cnt=1;
        res=temx+temy+cnt;
        cout<<res<<endl;
    }
}