// Recursive fibonacci function.
#include <iostream>
     
using std::cout;
using std::cin;
using std::endl;
     
unsigned long fibonacci( unsigned long ); // function prototype
    
int main()
{
  unsigned long result, number;
    
  // obtain integer from user
  cout << "Enter an integer: ";
  cin >> number;
    
  // calculate fibonacci value for number input by user
  result = fibonacci( number );
    
  // display result
  cout << "Fibonacci(" << number << ") = " << result << endl;
    
  return 0;  // indicates successful termination
    
} // end main
    
// recursive definition of function fibonacci        
unsigned long fibonacci( unsigned long n )           
{                                                    
  // base case                                      
  if ( n == 0 || n == 1 )                           
    return n;                                      
                                                         
  // recursive step                                 
  else                                              
    return fibonacci( n - 1 ) + fibonacci( n - 2 );
                                                         
} // end function fibonacci