1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<algorithm>
 6 using namespace std;
 7 struct Node{
 8     int x,y;
 9     friend int operator < (Node a,Node b){
10         if(a.x<b.x||(a.x==b.x&&a.y<b.y))return 1;
11         else return 0;
12     } 
13 };
14 int chaji(Node a,Node b,Node c){
15     return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
16 }
17 Node a[110],ans[110];
18 int main(){
19     int N,m;
20     scanf("%d",&N);
21     while(N--){
22         scanf("%d",&m);
23         for(int i=0;i<m;i++)scanf("%d%d",&a[i].x,&a[i].y);
24         sort(a,a+m);
25         int k=0;
26         for(int i=0;i<m;i++){
27             while(k>1&&chaji(ans[k-2],ans[k-1],a[i])<=0)k--;
28             ans[k++]=a[i];
29         }
30         int t=k;
31         for(int i=m-1;i>=0;i--){
32             while(k>t&&chaji(ans[k-2],ans[k-1],a[i])<=0)k--;
33             ans[k++]=a[i];
34         }
35         k--;
36         sort(ans,ans+k);
37         for(int i=0;i<k;i++)printf("%d %d\n",ans[i].x,ans[i].y);
38     }
39     return 0;
40 }