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1. Warmup
"I'm thinking of five letters," I smiled.
"Are they ... G, B, K, J, and N?" you asked.
"No, none of those."
"C, X, Q, A, and N?"
I gulped. "Four of those."
"K, I, Y, T, and M?"
"One of those."
"S, D, Z, I, and K?"
"One of those. Now that's enough guessing; you have enough information to...