????????
      +---------
PPFLQ | XCXXXUUQ
       -PPFLQ
        =====
         QPQNU
        -PPFLQ
         =====
         CFQFXU
        -MXPCQF
         ======
          YMRNUQ
         -WLPQFF
          ======
          ??????

base: 12
letters: CFLMNPQRUWXY
difficulty: medium