[UVA][前序] 11108 - Tautology
Problem D: Tautology
WFF 'N PROOF is a logic game played with dice. Each die has six faces representing
some subset of the possible symbols K, A, N, C, E, p, q, r, s, t.
A Well-formed formula (WFF) is any string of these symbols obeying the following
rules:
p, q, r, s, and...
