#874. Recurrent sequence (×2 + -1)
a₁ = 1, aₙ = aₙ₋₁ · 2 + -1. You get n. Find aₙ.
### Input
One integer n (1 ≤ n ≤ 40).
### Output
A number.
Examples
Input
39
Output
1
Input
15
Output
1
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.