# Compute n-factorial using a function

# Compute the value of n factor
# Parameters:
#   n: an integer greater than or equal to 0
# Returns: n-factorial
def factorial(n):
  factor = n
  result = 1
  while factor > 0:
    result = result * factor
    factor = factor - 1

  return result

# Compute the factorial of a number entered by the user
def main():
  # Read the input from the user
  a = int(input("Enter a non-negative integer: "))
  
  # Compute the factorial
  result = factorial(a)

  # Display the result
  print("result is", result)

main()