#include <iostream>


using namespace std;

int main()
{   int max = 30, evenNum;
	/* Odd or even? */
	if((max % 2)==1) 
		evenNum = 0; 
	else 
		evenNum = 1;
    if(evenNum==1)
    {
		for(int x=1; x<=max; x++)
	   	{
	       {
	   	   cout << x << " " << (max/2)+x << endl;
		   if (x >= (max/2))
		      break;
	       } 
	   	}   
    } 
    else
		for(int x=1; x<=(max+1); x++)
	   	{
	       {
	   	   if(x == ((max+1)/2)) 
	   	      cout << x << endl;
	   	   else
	   	      cout << x << " " << ((max+1)/2)+x << endl;
		   if (x >= ((max+1)/2))
		      break;
	       } 
	   	}   
    
	return 0;
}