Four gears are in constant mesh with each other. Gear A meshes only with Gear B, B meshes with A and C, C meshes with B and D, and D meshes only with C, like this:

A B C D

Gears A, B, C, and D have 35, 27, 84, and 34 teeth, respectively.

If a vertical stripe is painted on each gear, what is the minimum number of revolutions (>0) gear A would have to make before the four stripes are vertical again?