FUNCTION z2el,z,UP=up,LOW=lo

IF N_ELEMENTS(up) EQ 0 THEN up=-1
IF N_ELEMENTS(lo) EQ 0 THEN lo=-1
IF (up EQ -1) AND (lo EQ -1) THEN up=1
IF (lo EQ 1) THEN up=0
IF (lo EQ 0) THEN up=1
IF (up EQ 0) THEN lo=1
IF (up NE 0) THEN BEGIN 
    lo=0
    up=1
ENDIF

elements_up=up
@elements

RETURN,elements(z)
END