http://acm.hdu.edu.cn/showproblem.php?pid=2018
#include<iostream>
#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
using namespace std; int main()
{
int f[];
memset(f,,sizeof(f));
f[]=;f[]=;f[]=;f[]=;
for(int i=;i<;i++)
{
f[i]=f[i-]+f[i-];
}
int n;
while(cin>>n)
{
if(n==)
break;
printf("%d\n",f[n]);
}
return ;
}