#include<stdio.h>

int isPrime(int,int);

int main(){

    int num,prime;

    printf("Enter a positive number: ");
    scanf("%d",&num);

    prime = isPrime(num,num/2);

   if(prime==1)
        printf("%d is a prime number",num);
   else
      printf("%d is not a prime number",num);

   return 0;
}

int isPrime(int num,int i){

    if(i==1){
        return 1;
    }else{
       if(num%i==0)
         return 0;
       else
         isPrime(num,i-1);
    }
}