/in/foo.cc: In function 'int main()':
/in/foo.cc:45:12: error: conflicting declaration 'int a'
  int a[N], a;
            ^
/in/foo.cc:45:6: note: previous declaration as 'int a [10000]'
  int a[N], a;
      ^
/in/foo.cc:46:12: error: conflicting declaration 'int b'
  int b[N], b;
            ^
/in/foo.cc:46:6: note: previous declaration as 'int b [10000]'
  int b[N], b;
      ^
/in/foo.cc:47:12: error: 'na' was not declared in this scope
  Output(a, na);
            ^~
/in/foo.cc:48:12: error: 'nb' was not declared in this scope
  Output(a, nb);
            ^~