#include <stdio.h>

int is_odd(unsigned n);
int is_even(unsigned n);

int is_even(unsigned n)
{
    return n == 0 ? 1 : is_odd(n-1);
}

int is_odd(unsigned n)
{
    return n == 0 ? 0 : (n == 1 ? 1 : is_even(n-1));
}

int main(void)
{
    unsigned num;
    
	num = 17;
    printf("%u is %s\n", num, is_even(num) ? "even" : "odd");
    
    return 0;
}