/in/foo.cc: In function 'bool check(const string&)':
/in/foo.cc:5:34: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if (s.length() == 1 && "0" <= s && s <= "9" || s.length() == 2 && "10" <= s && s <= "99" || s.length() == 3 && "100" <= s && s <= "255")return true;
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
/in/foo.cc:5:124: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if (s.length() == 1 && "0" <= s && s <= "9" || s.length() == 2 && "10" <= s && s <= "99" || s.length() == 3 && "100" <= s && s <= "255")return true;
                                                                                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
/in/foo.cc: In function 'bool isLeagal(const string&)':
/in/foo.cc:10:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i<s.length(); ++i) {
                  ~^~~~~~~~~~~