#include <iostream>
  
 using  namespace  std;
  
 void  f(int & a)
 {
    a = a + 1;
 }
  
 int main(int argc, char *argv[])
 {
    int k = 7;
  
    cout << "before f( ): " << k << endl; // Prints: 7
  
    f(k);
  
    cout << "after  f( ): " << k << endl; // Prints: 7 (k unchanged !)   
 }