[aditya.shevade]

Easy. Check this out.

#include<iostream>

using namespace std;

main()
{
	int a, b;
	
	cout << "Enter A and B" << endl;
	cout << "a = ";
	cin >> a;
	cout << endl << "b = ";	
	cin >> b;
	
	a = ((b - a) + (b = a));
	
	cout << endl << "a = " << a << endl;
	cout << "b = " << b;
	
	return 0;
	
}

EDIT : Output :-

EXECUTING:
/home/aditya/test 
----------------------------------------------
Enter A and B
a = 12

b = 23

a = 23
b = 12
----------------------------------------------
Program exited successfully with errcode (0)
Press the Enter key to close this terminal ...