http://oj.ecustacm.cn/problem.php?id=1255

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<string>
using namespace std;
int main(void)
{
    
    
	int n;
	while(cin>>n)
	{
    
    
		int sum=n;//喝的瓶数 
		int temp=n;//瓶盖数 
		while(temp>=3)
		{
    
    
			sum+=temp/3;
			temp=temp/3+temp%3; 
		}
		cout<<sum<<endl;
	} 
	return 0;
}

//喝三瓶可以兑换1瓶  相当于又补了一瓶  即每次减2瓶
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<string>
using namespace std;
int main(void)
{
    
    
	int n;
	while(cin>>n)
	{
    
    
		int ans=0;
		while(n>=3)//当前总的瓶数  
		{
    
    
			n=n-2;
			ans=ans+3;
		}
		cout<<ans+n<<endl;
	} 
	return 0;
}