How do i input the alarm code on the 1991 bmw 525 I to turn the radio on?

I have a 5 digit code but the BMW only accepts 4 digitsHow do i input the alarm code on the 1991 bmw 525 I to turn the radio on?You need to take Stereo's sn down and get the code from the dealer. More than likely you have the wrong code, just bring proof of ownership and they should take care of you.