Create a page with one input fields,
Clicking on input should show a dropdown with 3 values (1,2,3)
Selecting an item should from first dropdown should show second dropdown with values depending on selection.
i.e. selecting 1 should show second dropdown with values 1.1, 1.2, 1.3
Selecting 2 should show dropdown with values 2.1, 2.2, 2.3
Selecting 3 should show dropdown with values 3.1, 3.2, 3.2
now after selecting a value in 2nd dropdown, that value has to be placed into input field.
if input field has a value already, no need to perform this operation.
if its value is empty, however this has to be performed.