int LF(int n)  //此函數返回n的最小非1因子
{
  if(n%2==0)
    return 2;
  int i=3;
  while(i<=n)
  {
    if(n%i==0)
      return i;
    i=i+2;
  }
  return n;
}

void main()
{
  int n,i;
  output "驗證歌德巴赫猜想\n";
  while()
  {
    output "請輸入一個大于2的偶數：";
    input n;
    if(n==0)
      exit;
    while(n<=2 || n%2!=0)
    {
      output "輸入錯誤！請輸入一個大于2的偶數：";
      input n;
      if(n==0)
        exit;
    }
    if(n==4)
      output "4 = 2+2\n";
    else
    {
      i=n/2;
      if(i%2==0)
        i=i-1;
      while()
      {
        if(i==LF(i) && n-i==LF(n-i))
        {
          output n," = ",i,"+",n-i,"\n";
          break;
        }
        i=i-2;
      }
    }
  }
}