/* A program that prints all primes smaller than a number */

#include <stdio.h>
#include <math.h>

int is_prime(int num)
{
  int i, sq;
  sq = (int) sqrt(num);
  for (i = 2 ; i <= sq; i++) {
    if (num % i == 0)
        return 0;
  }
  return 1;
}

int main()
{
  int i, j, sq, last;
  printf("Enetr a number: ");
  if (scanf("%d", &last) != 1) {
    printf("ERROR: failed to read a number!\n");
    return -1;
  }
  for (i = 2; i <= last; i++) {
    if (is_prime(i) == 1)
      printf("the number %d is prime\n", i);  
  }
  return 0;
}