/in/foo.cc: In function 'int ask(int, int)':
/in/foo.cc:27:6: warning: unused variable 'len' [-Wunused-variable]
  int len=ed-beg+1,root=0;
      ^~~
/in/foo.cc:34:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^