????????
     +---------
EXPE | ENXFNFFE
      -XEMXN
       =====
        XANPF
       -MFFMX
        =====
         ANXNF
        - EXPE
         =====
          XPNAE
         -MFFMX
          =====
          ?????

base: 7
letters: AEFMNPX
difficulty: intermediate