/in/foo.cc: In function 'int lca::main()':
/in/foo.cc:131:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:136:7: warning: unused variable 'flag' [-Wunused-variable]
  bool flag = true;
       ^~~~
/in/foo.cc: In function 'void lca::erase(int)':
/in/foo.cc:98:10: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   int l, r;
          ^