P1096 Hanoi双塔问题

// P1096 Hanoi双塔问题.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

#include <iostream> 
#include<cstdio>
using namespace std;

int main()
{
	int n;
	//freopen("hanoi.in", "r", stdin);
	//freopen("hanoi.out", "w", stdout);
	//cin >> n;
	scanf("%d", &n);
	int sum = 0, m;
	for (int i = 1; i <= n; i++)
	{
		m = 2;
		for (int k = 1; k < i; k++)
		{
			m *= 2;
		}
		sum += m;
	}
	printf("%d", sum);
	//cout << sum << endl;
	//fclose(stdin);
	//fclose(stdout);
	return 0;
}