#include <stdio.h>
int main(void){
  int i,n,residue;
  printf("Input number:");
  scanf("%d",&n);
  residue=1;
  for (i=n-1;i>1;i--){
    //    printf("%4d",i);
    if (n%i==0){
      residue=0;
    }
  }
  if (residue==1){
    printf("\n%d is a prime number.\n",n);
  } else {
    printf("\n%d is not a prime number.\n",n);
  }
  return 0;
}