/* example of using XOR to swap */
#include <stdio.h>
#define S(a,b) { (a)^=(b); (b)^=(a); (a)^=(b); }
int main() {
    int a=5, b=4;
    printf("%d %d\n", a, b);
    a^=b;
    b^=a;
    a^=b;
    printf("%d %d\n", a, b);
    S(a,b);
    printf("%d %d\n", a, b);
    return 0;
}