#include <iostream>
const double PI=3.14;
using namespace std;

double fcir_l(double r)
{
   double cir_l;
   cir_l=2*PI*r;
   return cir_l;
}

double fcir_s(double r)
{
   double cir_s;
   cir_s=PI*r*r;
   return cir_s;
}

int main()
{
  double radius, cir_l,cir_s;
  int i=0;
  cout<<"Please input radius:"<<endl;
  cin>>radius;
  cout<<"please choose number:1.perimeter 2.area"<<endl;
  cin>>i;
  switch(i)
  {
  case 1:
      cir_l=fcir_l(radius);
  cout<<"the perimeter is:"<<cir_l<<endl;
  break;

  case 2:
      cir_s=fcir_s(radius);
  cout<<"the area is:"<<cir_s<<endl;
  break;
  }
return 0;
 
}