母牛的故事

#include<stdio.h>
main()
{
    int fun(int n);
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        if(n==0)break;
        printf("%d\n",fun(n));
    }
}
int fun(int n)
{
    if(n<=3)
        return n;
    else return fun(n-1)+fun(n-3);
}