foo.cc: In function 'int main()':
foo.cc:9:6: warning: 'a' is used uninitialized in this function [-Wuninitialized]
  i=10*a+b;
    ~~^~
foo.cc:9:3: warning: 'b' is used uninitialized in this function [-Wuninitialized]
  i=10*a+b;
  ~^~~~~~~

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