????????
      +---------
AFNUA | NFHNFTGJ
       -JHNTJ
        =====
         QJUQT
        -AFNUA
         =====
         GAUJJG
        -GFGJNT
         ======
          GANJNJ
         -GFGJNT
          ======
          ??????

base: 10
letters: AFGHJNQRTU
difficulty: easy
missing: R