What is correct output for follwing code ?1

#include<stdio.h>
#include<conio.h>
main()
{
     int a=10, b=20;
     clrscr();
     printf("Before swapping a=%d b=%d",a,b);
     a=a+b;
     b=a-b;
     a=a-b;
     printf("nAfter swapping a=%d b=%d",a,b);
     getch();
}