# In mathematics, the factorial of an integer n, denoted by n! is the following
# product:
# n!=1×2×...×n
# For the given integer n
# calculate the value n!. Don't use math module in this exercise.

# n=int(input("введите число: "))
# factorial=1
# if n<0:
#   print("error")
# if n==0:
#   print("1")
# else:
#   for i in range(1,n+1):
#      factorial=factorial*i
# print(factorial) 