Do the math, 100 x 2 = 200, then x2 = 400, in the 15's time it's going to be 1.5 million.
Life does not go like math equations; If you buy a $ 100 bitcoin since 2009, you will be rich in less than ten years.
Might be doable in less than a month!
This is the real question of how to maximize your profits in the fastest possible time. Mark Zuckerberg can double his money and reach the amount of one million dollars in less than two months while normal humans need much longer.
Try your luck and invest in Bitcoin for a long time