class Factorial_G {
  static iterative ( BigInteger n ) {
    if ( n < 0G ) { throw new FactorialIllegalArgumentException ( 'Parameter must be a non-negative integer.' ) }
    def total = 1G
    if ( n > 1G ) { for ( i in 2G..n ) { total *= i } }
    total
  }
  static iterative ( Integer n ) { iterative ( new BigInteger ( n.toString ( ) ) ) }
  static iterative ( Long n ) { iterative ( new BigInteger ( n.toString ( ) ) ) }
  static recursive ( BigInteger n ) {
    if ( n < 0G ) { throw new FactorialIllegalArgumentException ( 'Parameter must be a non-negative integer.' ) }
    n <= 1G ? 1G : n * recursive ( n - 1 )
  }
  static recursive ( Integer n ) { recursive ( new BigInteger ( n.toString ( ) ) ) }
  static recursive ( Long n ) { recursive ( new BigInteger ( n.toString ( ) ) ) }
  static tailRecursive ( BigInteger n ) {
    if ( n < 0G ) { throw new FactorialIllegalArgumentException ( 'Parameter must be a non-negative integer.' ) }
    def iterate
    iterate = { BigInteger i , BigInteger result -> i < 2G ? result : iterate ( i - 1G , result * i ) }
    iterate ( n , 1G )
  }
  static tailRecursive ( Integer n ) { tailRecursive ( new BigInteger ( n.toString ( ) ) ) }
  static tailRecursive ( Long n ) { tailRecursive ( new BigInteger ( n.toString ( ) ) ) }
}