42. Train Crossing Time

Difficulty: easy · Math

Problem

A train must cover a total distance of 800 metres (a 400 m stretch of track plus a 400 m bridge). Given its speed in km/hr, compute the time it takes in seconds. Convert the speed to metres per second (multiply by `5/18`) and divide the distance by it; equivalently the time is `(800 / speed) * (18 / 5)` seconds. Print the time rounded to 2 decimal places (a third decimal of exactly 5 followed by nothing rounds up).

Input

A single line containing the integer `speed` in km/hr.

Output

Print the time in seconds with exactly two digits after the decimal point.

Example 1

Input:
72
Output:
40.00

Explanation: 72 km/hr is 20 m/s, and 800 / 20 = 40 seconds, printed as 40.00.

Example 2

Input:
7
Output:
411.43

Explanation: 2880 / 7 = 411.428..., which rounds to 411.43.

Constraints

- 1 <= speed <= 10^6

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