Day 17 Assignment 3 - Prime Number or Not

#include <stdio.h>

int main() {
    int num, i, flag = 0;
    
    printf("Enter a positive integer: ");
    scanf("%d", &num);
    
    if (num <= 1) {
        printf("NOT PRIME\n");
        return 0;
    }
    
    for (i = 2; i <= num/2; ++i) {
        if (num % i == 0) {
            flag = 1;
            break;
        }
    }
    
    if (flag == 0)
        printf("PRIME\n");
    else
        printf("NOT PRIME\n");
    
    return 0;
}