Context: Playing Lost Mines of Phandelven with a group of friends online. We were about to get fireballed

Langlock: I cast counterspell

DM: Well, it won’t work because you only have a sixty foot range. This guy is fifty feet away and thirty feet up.

Me: Wait, hold on, hold on. Gotta check something real quick, what is 50 squared plus 30 squared!?

*Cue the party quickly using Pythagorean theorum in order to prove that he is within range*

Considious: 58.309! He is within range

DM, clearly defeated: Alright, well. You cast counterspell and stop what you recognize as a fireball

*Cue everyone making sighs of relief and surprise*

Me: Langlock is the MVP

Considious: Phew, we dodged a TPK

Me (Red Dragonborn Paladin) Well, you all might have died. I would have been fine.