#include <iostream>
______(1)______
#include <cmath>
using namespace std;
int main(){
double x,y;
_____(2)______;
switch(____(3)_____)
{
case 8:y=pow(x,2); break;
case 7:y=2*x/3+4; break;
case 5:
case 6: _____(4)_____; break;
default: y=0;
}
cout<<fixed<<setprecision(2)<<"y="<<y;
}