Addition without using third variable

#include<stdio.h>
 
main()
{
   int a = 1, b = 2;
 
   /* Storing result of addition in variable a */
 
   a = a + b;
 
   /* Not recommended because original value of a is lost  
    * and you may be using it some where in code considering it 
    * as it was entered by the user. 
    */
 
   printf("Sum of a and b = %d\n", a);
 
   return 0;
}