????????
      +---------
PUTGJ | TLJFUPNP
       -PUTGJ
        =====
         WULXP
        -PUTGJ
         =====
         MWPYRN
        -MFXUUH
         ======
          FYQPNP
         -XPQXJT
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium