B. Bespin
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Cloud City floats in the sky of Bespin, an immense gas giant. The city is planning a supply run and has $$$n$$$ distinct cargo ships available. The city must dispatch a fleet for the mission, but Imperial patrol patterns mean that the fleet must contain an odd number of ships (because an even number of ships would be too easy to detect). At least one ship must be in each fleet.

How many different fleets can be assembled?

Input

A single integer $$$n$$$ $$$(1 \leq n \leq 60)$$$, the number of distinct ships available.

Output

A single integer: the number of valid fleets.

Example
Input
3
Output
4
Note

If there are $$$n=3$$$ ships, the only possible odd-numbered fleets are of sizes 1 and 3. For a fleet with one ship, there are three unique fleets, one per unique ship. For a fleet with three ships, there is only one possible fleet: selecting all three ships. So, $$$3+1=4$$$ unique fleets are possible.