Left pad varchar to certain length in sql server

Left pad varchar to certain length in sql server

I want to left pad int number with 12 digits as 0 and starting with
character as 'P'
E.g if number is 345 Then output should be 'P00000000345'
My Code :
Declare @a int
Set @a =8756
Select Right('P00000000000' +Cast(@a As Varchar(11)),12)
DB : SQL SERVER 2008