Upon inputting each cow ~i~'s moo frequency ~M_i~, we'll need to determine whether it's a power-of-~2~ multiple of ~F~, and output the number ~i~ if it's not.

One way to check this is to initialize a variable ~x~ to be equal to ~F~, and then repeatedly multiply ~x~ by ~2~ while checking if it's equal to ~M_i~ at each iteration. If we do find a value of ~x~ which is equal to ~M_i~, then we know that cow ~i~ isn't an imposter, and we'll want to skip over it. On the other hand, if ~x~ never becomes equal to ~M_i~ and instead gets to be larger than ~M_i~, then we know that cow ~i~ is an alien imposter.