The Peak of the Bell Curve

You're building the plotting component for Whetcode Learn's statistics course. Each panel draws a bell curve centred on 0, and the vertical axis has to be scaled to that curve's tallest point, so the shape fills the panel instead of being clipped at the top or squashed into the bottom inch. Every panel picks its own standard deviation — the course walks students from a wide curve to a narrow one — so the height cannot be settled once and reused.

The curve is symmetric and peaks at its centre, so the height you need is the density at x = 0. A colleague has hard-coded 1 for it, on the grounds that the curve "adds up to 1" — the panels currently render the bell as a low bump with a lot of white space above it.

Task: Print the height of the density curve at its centre, rounded to 4 decimals.

Input

One line holding the curve's standard deviation, a decimal number greater than 0. The mean is always 0.

Output

One line holding the peak height, rounded to 4 decimals and printed the way Python prints a float.

Example:

Input:
1

Output:
0.3989