Transact SQL :: Function To Find Last Date Of Month One Year Ago - RETURNS ERROR

I've written sql code which takes a date and finds the Last Day of the Month one year ago. For example,  it takes the date '2015-04-17' and returns the date '2014-04-30'. The code works fine in a query. Now I'm trying to turn this into a function. However, when I try to create the function I get the error:

Operand type clash: date is incompatible with int

Why is this error being returned?

Here is my function:

CREATE FUNCTION dbo.zEOM_LY_D(@Input Date)
       RETURNS date
AS
BEGIN;
  DECLARE @Result date;
  SET @Result =  convert(DATE, DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,dateadd(m, -11, @Input)+1),0)),101)
    RETURN @Result;
END;