Time Limit: 500MS

Memory Limit: 65536KB

64bit IO Format: %I64d & %I64u

 

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 
         
          #include 
          
           int main(){	long long n;	while (scanf("%lld", &n) != EOF) {		long long ans = 2;		if (n == 0)	continue;		for (long long i = 2; i <= n; i++) {			ans = ans + pow(2 , i);		}		printf("%lld\n", ans);	}	return 0;}