IBAN mask with label

I m trying to mask an input field for IBAN entry. I tried to use RobinHerbots/Inputmask in my angular project but couldnt really manage to get exactly what i need. Somehow library is transforming the “IBAN” to “IB_N”. Any ideas how could i use the letter “A” ? (screenshots)

what i get

what i tried

ngAfterViewInit(): void {
      let selector = document.getElementById('sofortIban');
      Inputmask({'mask': "IBAN" +
          'AA99-9999-9999-9999-9999-99', clearMaskOnLostFocus: false, rightAlign: true}).mask(selector);
    }

https://stackblitz.com/edit/angular-ph3dmv?embed=1&file=src/app/app.component.ts

Answer

Seem to have fixed it by writing "IB\AN" probably that A is reserved for something or other