# Factoriale
# 0! = 1 		(da! este adevarat)
# 1! = 1
# 2! = 1 * 2
# 3! = 1 * 2 * 3
# 4! = 1 * 2 * 3 * 4
# :
# :
# n! = 1 * 2 ** 3 * 4 * ... * n-1 * n


def function(param):
      if param < 0:
        return None
      if param < 2:
        return 1
    
      var = 1			# variabila declarata in interiorul functiei
      for i in range(2, param + 1):
        var *= i
      return var                # definitia functiei se termina aici

for param in range(1, 6): 	# test
      print(param, function(param))
# rezultat: 1 1
#           2 2
#           3 6
#           4 24
#           5 120