杭电2018 母牛的故事

#include<stdio.h>int main(){    int i,n,a[100];    while(scanf("%d",&n)!=EOF)    {        a[1]=1;a[2]=2;a[3]=3;        if(n==0)break;    if(n>=4)    {        for(i=4;i<=n;i++)        {            a[i]=a[i-1]+a[i-3];        }        printf("%d\n",a[n]);    }    else if(n>=3) printf("%d\n",a[n]);    else if(n>=2) printf("%d\n",a[n]);    else if(n>=1) printf("%d\n",a[n]);    }    return 0;}