/in/foo.cc: In function 'void biao()':
/in/foo.cc:28:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(ll i=0;i<s.size();i++)
             ~^~~~~~~~~
/in/foo.cc: In function 'll ri(char)':
/in/foo.cc:16:1: warning: control reaches end of non-void function [-Wreturn-type]
 } 
 ^
/in/foo.cc: In function 'll suan(ll, char, ll)':
/in/foo.cc:24:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^