ipsos-components/src/material-examples/form-field-custom-control/form-field-custom-control-example.html

Material Design components for Angular

<div [formGroup]="parts">
  <input class="area" formControlName="area" size="3">
  <span>&ndash;</span>
  <input class="exchange" formControlName="exchange" size="3">
  <span>&ndash;</span>
  <input class="subscriber" formControlName="subscriber" size="4">
</div>