Swap 3 integers without any fourth variables

eg.                               x = 10         y = 20     z = 30

output :                    x = 30         y = 10     z =20

#include<iostream.h>

#include<conio.h>

# include <stdio.h>

void main()

{

int x, y, z;

cout<< "\n Enter 3 nos :";

cin>> x >> y >> z ;

cout<<"\n Old values :\n";

cout << "x = " << x << " y = " <<< "z = " << z ;

x = x+y+z;

y = x - (y+z);

z = x - (y+z);

x = x - (y + z);

cout<<"\n New values :\n";

cout << "x = " << x << " y = " <<< "z = " << z ;

getch();

}