foo.c:7:1: error: unknown type name 'BT'
    7 | BT*1*2*3*4*5*6*7;
      | ^~
foo.c:7:4: error: expected identifier or '(' before numeric constant
    7 | BT*1*2*3*4*5*6*7;
      |    ^
foo.c:8:4: error: expected identifier or '(' before numeric constant
    8 |    7*!!!!!!!
      |    ^

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