题解 | #[NOIP2007]Hanoi双塔问题#

import java.math.BigInteger;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        BigInteger ans = BigInteger.valueOf(2);
        ans = ans.pow(n).add(BigInteger.valueOf(-1));
        System.out.println(ans.add(ans));
    }
}