#include "library.h"
#include <iomanip>

bool close_enough(const double a, const double b)
{ const double diff = fabs(a - b) / max(a, b);
  if (diff < 1.0e-9)
    return true;
  return false; }

double square_root(const double n, const double min, const double max)
{ // cout << "min = " << setprecision(20) << min << ", max = " << setprecision(20) << max << "\n";
  if (min > max)
    return -1;
  const double middle = (min + max) / 2;
  const double found = middle * middle;
  if (close_enough(n, found))
    return middle;
  if (n < found)
    return square_root(n, min, middle);
  return square_root(n, middle, max); }

void main()
{ cout << "Enter a square: ";
  const double n = read_double();
  const double s = square_root(n, 0, n + 1);
  cout << "The square root of " << n << " is " << setprecision(20) << s << "\n";
  cout << "correct answer is " << setprecision(20) << sqrt(n) << "\n"; }