2.1.cpp

#include <iostream>
using namespace std;

bool fibon_elem(int ,int&);
int main()
{
	int pos, elem;
	char ch;
	bool more = true;

	while (more)
	{
		cout << "Please enter a position:";
		cin >> pos;

		if (fibon_elem(pos,elem))
			cout << "elemment # " << pos
				 << " is " << elem << endl;
		else
			cout << "Sorry, Count not calculate element"
				<< pos << endl;
		cout << "Do you want to continie (y/n):";
		cin >> ch;
		if (ch != 'y' && ch!= 'Y')
			more = false;
	}
	return 0;
}

bool fibon_elem (int pos, int& elem)
{
	if (pos <=0 || pos >1024)
		{ elem =0; return false; }
	elem = 1;
	int n_2 = 1;
	int n_1 = 1;

	for (int ix = 3; ix <= pos; ++ix)
	{
		elem = n_2 + n_1;
		n_2 = n_1;
		n_1 = elem;
	}
	return true;
}