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)

import sys
import math as mas

n=int(input())
a=1
for i in range(n):a*=i+1
print(a)

#for i in sys.stdin:
#	a,b=map(int,i.split())
#	print(gcd(a,b),lcm(a,b))