/in/foo.cc: In function 'void dp()':
/in/foo.cc:33:14: warning: variable 'l' set but not used [-Wunused-but-set-variable]
  int cur,pre,l,r;
              ^
/in/foo.cc:33:16: warning: variable 'r' set but not used [-Wunused-but-set-variable]
  int cur,pre,l,r;
                ^