Calculated Column based on the other column which is of type choice in SharePoint list

I am very new to the whole SharePoint and excel formulas and I am in the process of learning.

I have a list in SharePoint in which I have multiple columns.

I want to create a calculated column based on the value provided in the other column.

My first column “Input Data” with multiple choice as Strings. “String1”, “String2”, “String3”
My second column “value” is a numeric column.

If I choose “String1”, in the “Input Data” column then in the “value” column, I want a value 1
if I choose “String2”, in the “Input Data” column then in the “value” column, I want a value 3
if I choose “String3”, in the “Input Data” column then in the “value” column, I want a value 6

How do I write this?

I was initially trying to do it with one value

=if(((inputData))=="string1", 1,0)

but does not work.