#include <iostream.h>

double areaOfDisk(double);

void main()
{
  cout << "expected value: 3.14159" << endl;
  cout << areaOfDisk(1) << endl;

  cout << "expected value: 102.0702591" << endl;
  cout << areaOfDisk(5.7) << endl;
}

double areaOfDisk(double radius)
{
  const double PI = 3.14159;

  return (PI * radius * radius);
}