HDU—OJ 、2013 蟠桃记

代码：

import java.util.Scanner;

public class Flat_Peach {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int n = scanner.nextInt();

            int sum = 1;
            for (int i = 1; i < n; i++) {
                sum = 2 * sum + 2;
            }
            System.out.println(sum);
        }
    }
}