foo.cc: In function ‘bool dfs(int&)’:
foo.cc:9:23: warning: unused variable ‘bl’ [-Wunused-variable]
    9 |         if(wl==0) int bl=dfs(wl);
      |                       ^~
foo.cc:10:23: warning: unused variable ‘bl’ [-Wunused-variable]
   10 |         if(wr==0) int bl=dfs(wr);
      |                       ^~
foo.cc:14:17: error: ‘bl’ was not declared in this scope; did you mean ‘dl’?
   14 |         return (bl&&br&& wl*dl==wr*dr);
      |                 ^~
      |                 dl
foo.cc:14:21: error: ‘br’ was not declared in this scope; did you mean ‘dr’?
   14 |         return (bl&&br&& wl*dl==wr*dr);
      |                     ^~
      |                     dr