foo.cc: In function 'int main()':
foo.cc:8:2: error: expected ';' before 'cin'
  cin>>a;
  ^
foo.cc:10:2: error: expected ';' before 'cin'
  cin>>b;
  ^
foo.cc:11:7: error: 'a' was not declared in this scope
  cin>>a+b%*a
       ^
foo.cc:11:9: error: 'b' was not declared in this scope
  cin>>a+b%*a
         ^

自豪的采用 HydroJudger 进行评测(github.com/hydro-dev/HydroJudger)