杭电ACM----2018母牛的故事

[cpp]
#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; 
 
        } 
    } 
 
} 

补充：软件开发 , C++ ,