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()
{
  output "defactor\n";
  int n,f;
  while()
  {
    output "please input a integer (input 0 to exit) ";
    input n;
    while(n<0)
    {
      output "error! please input a integer \
(input 0 to exit) ";
      input n;
    }
    if(n==0)
      break;
    output n," = ";
    while()
    {
      f=LF(n);
      if(f==n)
      {
        output f,"\n";
        break;
      }
      output f,"*";
      n=n/f;
    }
  }
}