text: #include <stdlib.h>
  #include <time.h>
  #include <stdio.h>
  /**
  * main - Prints the digit numbers 0-9
  *
  * Return: 0
  */
  int main(void)
  {
  	int i;
  	int j;
  	int k;
  	int l;
  
  	for (i = '0' ; i <= '9' ; i++)
  	{
  		for  (j = '0' ; j <= '8' ; j++)
  		{
  			for (k = i ; k <= '9' ; k++)
  			{
  				for (l = j + 1 ; l <= '9' ; l++)
  				{
  					putchar(i);
  					putchar(j);
  					putchar(' ');
  					putchar(k);
  					putchar(l);
  					if (!(i == '9' && j == '8' && k == '9' && l == '9'))
  					{
  						putchar(',');
  						putchar(' ');
  					}
  				}
  			}
  		}
  	}
  	putchar('\n');
  	return (0);
  }
  