/in/foo.cc: In function 'void endd(int, int)':
/in/foo.cc:34:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0; i<used.size(); i++) {
                  ~^~~~~~~~~~~~
/in/foo.cc: In function 'void dfs(int, int, int, int)':
/in/foo.cc:44:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0; i<used.size(); i++)
                      ~^~~~~~~~~~~~
/in/foo.cc: In function 'bool check(int, int, int)':
/in/foo.cc:32:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^