n=input()
fact=1
if n.isdigit()==True:
    n=int(n)

    for i in range(2,n+1):
        fact=fact*i                     #factorial
    print(fact)
else:
    print("invalid")
12a4853fcbd2008ddfda6125d8a7b6d064ce2414
<mask token>

<mask token>
if n.isdigit() == True:
    n = int(n)
    for i in range(2, n + 1):
        fact = fact * i
    print(fact)
else:
    print('invalid')

n = input()
fact = 1
if n.isdigit() == True:
    n = int(n)
    for i in range(2, n + 1):
        fact = fact * i
    print(fact)
else:
    print('invalid')

n=input()
fact=1
if n.isdigit()==True:
    n=int(n)

    for i in range(2,n+1):
        fact=fact*i                     #factorial
    print(fact)
else:
    print("invalid")