C :

#include<stdio.h>
int main()
{
  int n;
  while(scanf("%d",&n)&&n!=0)
    printf("%d\n",n/2);
return 0;
}

C++ :

#include<iostream>
using namespace std;

int caculate(int n)
{
	if(n<=2)
		return 0;
	else if(n==3&&n==4)
	{
		return 1;
	}
	else
	{
		if(n%2)
		{
			return (n-1)/2;
		}
		else
		{
			return n/2;
		}
	}
}

int main()
{
	int N;
	while(cin>>N)
	{
		int count=0;
		if(N<=0)
		{
			return 0;
		}
		else
		{
			count=caculate(N);
		}
		cout<<count<<endl;
	}
	return 0;
}

Java :

import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner input=new Scanner(System.in);
		int sum=0;
		while(true){
			int n=input.nextInt();
			if(n==0){
				break;
			}
			int left=n;
			while(left>=3){
				int yu=left%3;
				int kong=left/3;
				sum+=kong;
				left=yu+kong;
			}
			if(left==2){
				sum+=1;
			}
			System.out.println(sum);
			sum=0;
		}

	}

}

Python :

# coding=utf-8
sum1 = 0
while 1:
    a = int(input())
    if a==0:
        break
    while 1:
        b = a//3 #取整
        sum1 = sum1+b
        c = a%3  #取余
        if b+c>=3:
            a = b+c
        elif b+c==2:
            sum1 = sum1 + 1
            break
        else:
            break
    print(sum1)
    sum1 = 0