Problem:
Factorial

Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.

Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Sample Input

5

Output for the Sample Input

120

Solution in Python3 (judge verdict: Accepted)

s = int(input())
k = 1
for i in range(2,s+1):
    k *= i
print(k)