In abaqus manual 1.2.17 , the information is given how to put two material model together but my question is where should i put this code

if (cmname(1:4) .eq. 'MAT1') then
   call VUMAT_MAT1(argument_list)
else if (cmname(1:4) .eq. 'MAT2') then
   call VUMAT_MAT2(argument_list)
end if

beginning or inside the code I didn't understand that , because i am new at user material modeling in vumat.

hence if anyone please help me with that I will be thankful to you.