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

int main ( )
{
  double e;
  double r1;
  double r2;
  double s;
//
//  What is the number whose square root we want?
//
  printf ( "Enter S: " );
  scanf ( "%lf", &s );
//
//  R1 is our initial guess.
//
  r1 = 1.0;

  while ( 0.00000001 < fabs ( s - r1 * r1 ) )
  {
    r2 = s / r1;
    printf ( "  %24.16g  %24.16g  %g\n", r1, r2, fabs ( s - r1 * r1 ) );
    r1 = ( r1 + r2 ) / 2;
  }

  printf ( "\n" );
  printf ( "  Final guess is %24.16g\n", r1 );
  printf ( "  Exact value is %24.16g\n", sqrt ( s ) );

  return 0;
}