
/*
AizuOnline A1200
Title Goldbach's Conjecture

*/
#include <stdio.h>
// Select Below
//#include <stdlib.h>
//#include <string.h>
//#include <float.h>
//#include <math.h>
//#include <limits.h>
//Global data section
int n;


int primes[]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,
	      101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,
	      211,223,227,229,233,239,241};


//
int isprime(int n)
{
  int i;
  for(i=0;i<sizeof(primes)/sizeof(int);i++)
    if(n == primes[i])
      return(-1);
  else if(n % primes[i] ==0)
      return(0);
  return(-1);
}
main()
{
  int i,c;
  while(EOF != scanf("%d",&n) && n)
    {     
      c=0;
      for(i=2;i<=n/2;i++)
	{
	  if(isprime(i) && isprime(n-i))
	    c++;	    
	}
      printf("%d\n",c);
    }
return(0);
}