HDU 5366 The mook jong

题目：http://acm.hdu.edu.cn/showproblem.php?pid=5366

代码：

#include<stdio.h>
#include<string.h>

using namespace std;

int main()
{
    int a;
    __int64 b[100]={0,1,2,3,5,8,13};
    while(~scanf("%d",&a))
    {
        for(int i=3;i<=a;i++)
        {
            b[i]=b[i-1]+b[i-3]+1;        //too difficult
        }
        printf("%I64d\n",b[a]);
    }
}