#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define CUTOFF 0.0000000001


// Newton-Raphson iteration: x_{n+1} = x_n - (x^2 - c) / (2*x)
double nr(double c)
{
  double x_prev = 1.0;
  double x_current = x_prev - (x_prev * x_prev - c) / (2 * x_prev);
  double diff = fabs(x_prev - x_current);
  int count = 0;

  while(diff > CUTOFF)
    {
      x_current = x_prev - (x_prev * x_prev - c) / (2 * x_prev);
      diff = fabs(x_prev - x_current);
      x_prev = x_current;
      count++;
    }

  return(x_current);
}

int main(int argc, char *argv[])
{
  if(argc > 1)
    nr(atof(argv[1]));
}