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.

Example

Input

5

Output

120

inputFormat

Input

An integer n (1 ≤ n ≤ 20) in a line.

outputFormat

Output

Print the factorial of n in a line.

Example

Input

5

Output

120

样例

5

120