HDU 2018 母牛的故事

#include <stdio.h>
fun(int n)//递归，用递推会更简单
{
    if (n == 1)
        return 1;
    if (n == 2)
        return 2;
    if (n == 3)
        return 3;
    if (n == 4)
        return 4;
    else
        return fun(n-1) + fun(n-3);
}
int main()
{
    int n;
    while( scanf("%d",&n)!= EOF)
    {
        if (n == 0)
        break;
        int result = fun(n);
        printf("%d\n",result);
    }
    return 0;
}