????????
      +---------
UNTTQ | LFWPGLXU
       -THGGX
        =====
        PMFHFL
       - THGGX
        ======
         RMUJXX
        -PQNYNL
         ======
          WQGGJU
         -WJHUHT
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium