#include<iostream.h>


void circ(double radius)
{
  cout << (radius)* 2.0 * 3.14;

}  // end circ

int main()
{
  double d;
  cout << "input diameter ";  
  cin >> d;
  circ(d/2.0);

  cout << "input diameter ";  
  cin >> d;
  circ(d/2.0);


} // end main