#include <stdio.h>
#include <stdlib.h>

int isitprime(int index);

int main()
{
    int index;
    int result;

    for (index = 1; index <= 20; index++)
        {
            result = isitprime(index);

            if (result == 1)
                {
                    printf("%d is prime\n", index);
                }
            else if (result == 0)
                {
                    printf("%d is not prime\n", index);
                }
            else
                {
                    printf("Something went wrong\n");
                }
        }

    return 0;
}


int isitprime(int index)
{
    int i = 0;
    int divisors = 0;

    for (i = 1; i <= index; i++)
        {
            if ((index % i) == 0)
                {
                    divisors++;
                }
        }

    if (divisors == 2)
        {
            return 1;
        }
    else if (divisors != 2)
        {
            return 0;
        }
    else
        {
            return -1;
        }
}