View Code of Problem 3834

import java.math.BigInteger;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        int n;
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            n = sc.nextInt();
            BigInteger sum = new BigInteger("2");
            while(n!=1){
                sum = sum.multiply(BigInteger.valueOf(3)).subtract(BigInteger.ONE);
                n--;
            }
            System.out.println(sum);
        }
    }
}