Problem Description

Input Format

A single line containing a positive integer \( n \), where \( n \leq 20 \).

Output Format

Output the solution \( s \) in a single line (the number of digits in the solution does not exceed 200).

Sample Input and Output

Sample Input #1

1

Sample Output #1

2

Sample Input #2

2

Sample Output #2

4

见题面 Input 部分

见题面 Output 部分