#include <library.h>

double search(double wanted, double begin, double end)
{ if (end-begin < 0.0000000001)
    return begin;
  const double mid = (begin + end) / 2;
  if (wanted < mid * mid)
    return search(wanted, begin, mid);
  if (wanted > mid * mid)
    return search(wanted, mid, end);
  return mid; }

void main()
{ print("Enter a square: ");
  const double Q = read_double();
  const double pos = search(Q, 0, 1000000000);
  print(Q);
  if (pos == -1)
    print(" does not appear");
  else
  { print(" appears at position ");
    print(pos); }
  new_line(); }