CODEFORCES630C- Lucky Numbers（水题）

 Lucky Numbers

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

Submit Status

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

2

Output

6

#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]);} }