#include <iostream>
using namespace std;

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

int main(void)
{
 int x = 10, y = 20;
 cout << x << ',' << y << '\n';
 swap(x,y);
 cout << x << ',' << y << '\n';
 return 0;
}