/in/foo.c: In function 'main':
/in/foo.c:13:9: warning: 'b1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  B = b1 - '0';
      ~~~^~~~~
/in/foo.c:12:9: warning: 'a1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  A = a1 - '0';
      ~~~^~~~~