View Code of Problem 3692

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 res = new BigInteger("6");
            if(n==0){
                System.out.println(0);
            }else if(n==1){
                System.out.println(3);
            }else {
                for (int i = 2; i < n; i++) {
                    if (i % 2 == 0) {
                        res = res.multiply(BigInteger.valueOf(2)).subtract(BigInteger.valueOf(6));
                    } else {
                        res = res.multiply(BigInteger.valueOf(2)).add(BigInteger.valueOf(6));
                    }
                }
                System.out.println(res);
            }
        }
    }
}