Description

Using the formula e = 1 + 1/1! + 1/2! + 1/3! + ... + 1/n!, calculate the value of e.

Input Format

Input consists of a single line containing an integer n (2 ≤ n ≤ 15).

Output Format

Output consists of a single line containing the calculated value of e, printed with 10 decimal places.

Sample

10

2.7182818011