3 girls must insert 8 dildos, which hole will they spare?

The Penetration Puzzle

Enjoy..

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There were eight dildos arranged on a central table, assorted in size and shape, but each made of blue rubber and stood with glowing strips spiralling from base to tip. The room was plain and not especially large, with white tiled floors and a mirror at head height running around the perimeter of the white walls. The mirror was barely long enough to see down to one's shoulders, and only served to draw the eyes even more to the table of dildos. There was a single sealed steel door on one side of the...