> #include<iostream>
> using namespace std;
> int main()
> {
> 	int L=0,answer=0;
> 	while(cin>>L)
> 	{
> 		int i=0,k=-1;
> 		int f1=2, f2=4,f3,f4;
> 		if(L==1)     answer=f1;
> 		else if(L==2)answer=f2;
> 		else
> 		{  int H=(int)(((double)L-0.5)/2.0);
> 		   //cout<<"H="<<H<<endl;
> 			for(i=1;i<=H;i++)
> 		  {
> 			f3=f1+f2;
> 			f4=f2+f3+k;
> 			f1=f3;
> 			f2=f4;
> 			k=-k;
> 			//cout<<"f1="<<f1<<endl;
> 			//cout<<"f2="<<f2<<endl;
>              
> 		  }
> 	    if(L%2==1)answer=f1;
> 		else      answer=f2;
> 
> 
> 		}
> 		cout<<answer<<endl;
> 		
> 	}
> 	return 0;
> }