CODEFORCES630C- Lucky Numbers（水题）

原创于 2016-03-09 16:22:53 发布 · 653 阅读

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#水题 #找规律 #简单数学 #CODEFORCES630C #Lucky Numbers

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--简单数学--

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本文介绍了一个算法，用于生成由数字7和8组成的幸运数字，并计算在限定位数内可能生成的最大数量的独特幸运数字。该算法适用于税务办公室新大楼办公室编号的需求。

Lucky Numbers

Time Limit:500MS Memory Limit:65536KB 64bit IO Format:%I64d & %I64u

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Description

The numbers of all offices in the new building of the Tax Office of IT City will have lucky numbers.

Lucky number is a number that consists of digits 7 and 8 only. Find the maximum number of offices in the new building of the Tax Office given that a door-plate can hold a number not longer than n digits.

Input

The only line of input contains one integer n (1 ≤ n ≤ 55) — the maximum length of a number that a door-plate can hold.

Output

Output one integer — the maximum number of offices, than can have unique lucky numbers not longer than n digits.

Sample Input

Input

Output

#include<stdio.h>
#include<iostream>
#include<string.h>
#include<algorithm>
using namespace std;
__int64 a[60];
void dabiao()
{
	int i,j;
	a[1]=2;
	for(i=2;i<=60;i++)
	{
		long long  temp=1;
		for(j=1;j<=i;j++)
		{
			temp*=2;
		}
		a[i]=a[i-1]+temp;
	}
}
int main()
{
	dabiao();
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		printf("%I64d\n",a[n]);
	} 
}