#include <stdio.h>
 
// Function declaration
int isPrime(int num);
 
int main() {
    int number;
 
    // Input number
    printf("Enter a number: ");
    scanf("%d", &number);
 
    // Function call and result display
    if (isPrime(number))
        printf("%d is a prime number.\n", number);
    else
        printf("%d is not a prime number.\n", number);
 
    return 0;
}
 
// Function definition
int isPrime(int num) {
    int i;
 
    // Numbers less than or equal to 1 are not prime
    if (num <= 1)
        return 0;
 
    // Check for divisors
    for (i = 2; i <= num / 2; i++) {
        if (num % i == 0)
            return 0;   // Not prime
    }
 
    return 1;   // Prime
}