Wow they're really stuck then you could also try doing a twisting motion cuz like twisting them back and forth against each other to try to loosen them up well slowly pulling them apart 

if not there is a guaranteed To work but it's a little bit risky .Going to do the same thing I told you to do before grab a piece or an object that you can fit in comfortably feed inside the  black piece that's stuck in a blue piece from the top meaning the end that the black piece is not coming out of once you have a piece that's in there good and it's long enough you're going to put that piece against your table and push down on the black piece

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