# include <math.h>
# include <stdio.h>
# include <stdlib.h>
#
# include "middle_square.h"
#
/******************************************************************************/

long long int middle_square_next ( long long int s, long long int d )

/******************************************************************************/
/*
  Purpose:

    middle_square_next() computes the next middle square random value.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    13 September 2022

  Author:

    John Burkardt

  Reference:

    Brian Hayes,
    The Middle of the Square,
    08 August 2022,
    http://bit-player.org/

  Input:

    long long int s: the current seed, of no more than 2*D digits.

    long long int d: HALF the number of digits.  
    Typical values are 2, 3, or 4.

  Output:

    long long int middle_square, the next seed.
*/
{
  long long int divisor;
  long long int r;
/*
  Square.
*/
  r = s * s;
/*
  Drop last two digits.
*/
  divisor = ( long long int ) ( pow ( 10, d ) );

  r = ( r / divisor );
/*
  Drop all but last four digits.
*/
  divisor = ( long long int ) ( pow ( 10, 2 * d ) );

  r = ( r % divisor );

  return r;
}