#include<iostream>
using namespace std;
void swapNums(int &x, int &y)
{
    int z = x;
    x=y;
    y=z;
}
int main()
{
  int n1 = 10;
  int n2 = 20;
  cout<<"\nBefore swap: ";
  cout<<"\n"<<n1<<"\n"<<n2;
  swapNums(n1, n2);
  cout<<"\nAfter swap: ";
  cout<<"\n"<<n1<<"\n"<<n2;
  return 0;
}