杭电ACM----2018母牛的故事

#include <iostream>using namespace std;int main(){    int n;    int a[56]={0,1,2,3};    while(cin>>n&&n)    {        switch(n)        {            case 1:                cout<<a[n]<<endl;                break;            case 2:                cout<<a[n]<<endl;                break;            case 3:                cout<<a[n]<<endl;                break;            default:                    for(int i=4;i<56;i++)                    a[i]=a[i-1]+a[i-3];                    cout<<a[n]<<endl;                    break;        }    }}