Folding a Piece of Paper

Create a function that returns the thickness (in meters) of a piece of paper after folding it n number of times. The paper starts off with a thickness of 0.5mm.

Examples

num_layers(1) ➞ "0.001m"
# Paper folded once is 1mm (equal to 0.001m)

num_layers(4) ➞ "0.008m"
# Paper folded 4 times is 8mm (equal to 0.008m)

num_layers(21) ➞ "1048.576m"
# Paper folded 21 times is 1048576mm (equal to 1048.576m)

Notes

• There are 1000mm in a single meter.
• Don't round answers.