汽水瓶

常规解法，易于理解

import java.util.*;
public class Main{

  public static void main(String [] args)
  {
      Scanner sc=new Scanner(System.in);
      while(sc.hasNext())
      {
          int n=sc.nextInt();
          if(n==0)break;
          int res=0,qi=0,left=0;
          while(n>=3)
          {
              qi=n/3;
              res+=qi;
              n=n%3+qi;
          }
          if(n==1||n==0){
              System.out.println(res);
          }
          else if(n==2)
          {
              System.out.println(res+1);
          }

      }

  }
}