C. Lucky Numberstime limit per test0.5 secondsmemory limit per test64 megabytesinputstandard inputoutputstandard outputThe 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.InputThe only line of input contains one integer n (1 ≤ n ≤ 55) — the maximum length of a number that a door-plate can hold.OutputOutput one integer — the maximum number of offices, than can have unique lucky numbers not longer than n digits.ExamplesInput2Output6
Input2
Output6
['combinatorics', 'math', '*1100']