foo.cc: In function 'int main()':
foo.cc:17:6: warning: left operand of comma operator has no effect [-Wunused-value]
  if(z==2,x==AA,c==BB){
     ~^~~
foo.cc:17:11: warning: right operand of comma operator has no effect [-Wunused-value]
  if(z==2,x==AA,c==BB){
          ~^~~~
foo.cc:17:2: warning: 'BB' is used uninitialized in this function [-Wuninitialized]
  if(z==2,x==AA,c==BB){
  ^~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。