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

const double delta = 0.0005;

double mySqrt(double);

void main(void)
{
   double x;

   cout << " type a value of x : ";
   cin >> x;
   cout << endl;
   cout << " mySqrt(x) " << mySqrt(x) << endl;
   cout << " math sqrt(x) " << sqrt(x) << endl;
}

double mySqrt(double r)
{
   double NG, CG, diff;

   CG = r;
   NG = 0;
   diff = fabs(NG - CG);
   while (diff > delta)
   {
      NG = 0.5 * (CG + r / CG);
      diff = fabs(NG - CG);
      CG = NG;
   }
   return NG;
}