/in/foo.cc: In function 'void ch(int, int)':
/in/foo.cc:6:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(s.find('1')<st||s.find('1')>ed) ans+=5;
        ~~~~~~~~~~~^~~
/in/foo.cc:6:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(s.find('1')<st||s.find('1')>ed) ans+=5;
                        ~~~~~~~~~~~^~~
/in/foo.cc:7:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     else if(s.find('0')<st||s.find('0')>ed) ans+=2;
             ~~~~~~~~~~~^~~
/in/foo.cc:7:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     else if(s.find('0')<st||s.find('0')>ed) ans+=2;
                             ~~~~~~~~~~~^~~