#include <stdio.h>
 
double quwl ( double ) ;
 
int main ( void )
{
	printf ( "%.18f\n" , quwl ( 3 ) ) ;
 
 
	return 0 ;
}
 
double quwl ( double rad )
{
	auto double xN = 1 , xNplus1 = rad ;
 
	auto unsigned char i ;
 
	for ( i = 1 ; i < 10 ; i ++ )
	{
		xN = xNplus1 ;
		xNplus1 = 1 / ( 2 * xN ) * ( xN * xN + rad ) ;
	}
 
	return xNplus1 ;
}