#
#  Compute n-factorial for a value of n read from the user.
#

#
#  Read the value of n from the user.
#
n = int(input("Enter a non-negative integer: "))
original_n = n

#
#  Initialize result.
#
result = 1

#
#  While n is greater than 0...
#
while n > 0:
  #
  #  Multiply the result so far by the current value of n.
  #
  result = result * n

  #
  #  Decrease the value of n
  #
  n = n - 1

#
# Display the result.
#
print(f"{original_n} factorial is equal to {result}.")