/in/foo.cc: In function 'int main()':
/in/foo.cc:8:11: error: 'a' was not declared in this scope
     int b[a];
           ^
/in/foo.cc:11:10: error: 'b' was not declared in this scope
     cin>>b[i];
          ^
/in/foo.cc:13:8: error: 'b' was not declared in this scope
  int c=b[0];
        ^