#include <iostream.h>
#include <math.h>
#include <conio.h>


void pause (void) {

  cout << "Hit any key to continue...";
  getch ();

}


void main (void) {

  double D, G, X, radius, half_gap;

  cout << "Please enter D and G (in inches): ";
  cin >> D >> G;

  // a couple of useful quantities...
  radius = D / 2;
  half_gap = G / 2;

  // with these quantities, the formula is short and sweet...
  X = radius - sqrt((radius * radius) - (half_gap * half_gap));

  cout << "The wheel will drop " << X << " inches." << endl;

  //
  pause ();

}