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

bool checkPrime(int p, int *pptr){
  int sqrt_p = sqrt(p);
  for(int i = 0; i < sqrt_p; i++){
    if(p % *(pptr+i) == 0){return false;}
  }
  return true;
}

int main(){
  double max = pow(10,7);
  int pi_max = (int)(ceil(1.1*(max/log(max))));
  int primes[pi_max];
  primes[0] = 2;
  int *pptr = &primes[0];
  int count = 1;

  //calculate primes 
  for(int c = 3; c <= max; c+=2){
    if(checkPrime(c, pptr)){
      primes[count] = c;
      count++;
    }
  }

  //print primes
  printf("The set of all primes below %d is: ", (int)max);
  for (int i = 0; i < count; i++){
    printf("%d ", primes[i]);
  }
  return 0;
}