/*
想要换最多的汽水,就要厚脸皮,
每两个空瓶向老板借一瓶汽水,
喝完之后拿三个空瓶再换一瓶还给老板;
相当于自己每两个空瓶可以换到一瓶汽水
核心代码bottle/2
*/
import java.util.Scanner;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
while(sc.hasNextInt()){
int bottle = sc.nextInt();
if(bottle==0){
break;
}
System.out.println(bottle/2);
}
}
}