LEA SI,BUF
    MOV CX,SIZE
    CALL    INDEX
    RET
INDEX:  MOV DI,SI
    REPNE   SCASB
    JNE INDEXL
    MOV CX,DI
    SUB CX,SI
INDEXL: DEC CX
    RET
BUF DB  1,2,3,4,5,6,7,8,9,0
SIZE    EQU ($-BUF)/TYPE BUF