control panel has four lamps, A through D. 43 seconds after switch-on,
lamp A flashes briefly on then off. This will repeat every 43
47 seconds after switch on, lamp B will also flash briefly. It flashes again every 37 seconds thereafter.
C flashes 49 seconds after switch-on, then every 97 seconds.
57 seconds after switch-on, lamp D flashes, after which it flashes every 79 seconds.
Will all lamps ever be on at the same time? If so, when? How many times will each have flashed?