#include <iostream>

void swap(int &a, int &b) {
    a ^= b;
    b ^= a;
    a ^= b;
}
    

int main() {
    int a = 5;
    int b = 1;
    swap(a, b);
    std::cout << a << " " << b << std::endl;
    swap(a, a);
    std::cout << a << std::endl;
}