Lidar (LIght Detection And Ranging) is a remote sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light. The technique is similar to radar, in which radio waves are used instead of light. The distance is determined by measuring the time that elapses between the transmission of a pulse and the reception of the reflection.

Lidar works on the same principle as radar: a signal is transmitted and the reflection of it is captured again some time later. The difference between lidar and radar is that lidar makes use of a laser beam while radar uses radio waves. This laser beam allows the detection of much smaller objects, because the wavelength of radio waves is around 1 cm, while the laser light's wavelength is between 10 $$\mu m$$ and 250 nm. At this wavelength small objects will better reflect the waves.

The formula that is used for the determination of the distance to an object is: $d = \frac{c \cdot t}{2 \cdot n}$ In which case $$d$$ represents the distance to the object (in metres), $$t$$ the time (in seconds) that the laser beam needs to travel back and forth, $$c$$ the speed of light in vacuum (299792458 m/s) and $$n$$ the refractive index. In air, the refractive index equals 1.000277 under standard conditions.

### Input

A number $$t \in \mathbb{N}$$ representing time in nanoseconds. 1 nanosecond equals $$10^{-9}$$ seconds.

### Output

The distance $$d$$ (in metres) to the object (assuming standard air conditions).

### Example

Input:

100

Output:

14.985471924276975 metre