#include <iostream>
using namespace std;

void swap(int& x, int& y)
{
    int tmp = y;
    y = x;
    x = tmp;
}

int main()
{
    int a = 1, b = 20;
    cout << "a=" << a << ", b=" << b << endl;
    swap(a, b);
    cout << "a=" << a << ", b=" << b << endl;
}
