C program swap two number without using third variable

#include<stdio.h>
void main()
{
    int x,y;
    clrscr();
    printf("\nPlease Enter a Number (x):");
    scanf("%d",&x);
    printf("\nPlease Enter a Number (y):");
    scanf("%d",&y);
    printf("\n\nValues Before Swapping\nx=[%d]\ny=[%d]",x,y);
    x=x+y;
    y=x-y;
    x=x-y;
    printf("\n\nValues After Swapping\nx=[%d]\ny=[%d]",x,y);
    getch();
} 
                                

Please Enter a Number (x): 40
Please Enter a Number (y): 30
Values Before Swapping
x=[40]
y=[30]
Values After Swapping
x=[30]
y=[40]