#include <iostream>
using namespace std;
int doublebyValue(int);
void doublebyRef(int*);
void doublebyRefRef(int&);

main(){
  int val = 7;

  //val = doublebyValue(val);

  //doublebyRef(&val);

  doublebyRefRef(val);

  cout << val << endl;
}

int doublebyValue(int n){
  return n*2;
}

void doublebyRef(int *ptr){
  *ptr *= 2;
}

void doublebyRefRef(int &n){
  n *= 2;
}