????????
      +---------
RUWWU | UGJFUYJR
       -RUWWU
        =====
        XQFHMY
       -XJYMGH
        ======
         XYWYNJ
        -XUMULT
         ======
          XWMNWR
         -XTWTUU
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium
missing: P