~~~ #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; } } } ~~~