// counts to the number provided with even numbers using a recursive recursive algo
// written by Matthew Early, but hey this is a pretty common practice problem
// default compile:
//   compile in terminal with 'g++ recursive-even-counter.cpp'
//   run with './a.out' in terminal

#include <iostream>
#include <cstdlib>

using namespace std;

void counting(int x);

int main() {
	int x = 0;
	cout << "enter a number to count to evenly: ";
	cin >> x;
	counting(x);
	cout << endl;
}


void counting(int x) {
	if (x == 0) {
		cout << 0 << " ";
		return 0;
	}

	if (x < 0) { exit(-1); }

	if (x%2 == 0) {
		counting(x-1);
		cout << x << " ";
	} else {  //x is odd
		counting(x-1);
	}

}