stl to scl programing

Can anybody help me to program the following in SCL?

SET
SAVE
= L 2.5
A7d0: L 0
T #i
L #i
L 1
+I
T #i
CLR
A #a
JCN A7d1
SET
= #b
JU A7d2
A7d1: CLR
A #b
JCN A7d3
A #c
JCN A7d5
SET
= #d
JU A7d2
JU A7d5
A7d3: CLR
= #d
JU A7d6
A7d5: CLR
A #d
JCN A7d2
SET
= #a
A7d2: L #i
L 20
>I
JCN A7d0
A7d6: CLR
A L 2.5
SAVE
BE

I've tried like this
FUNCTION FC3001 : void
VAR_TEMP
i:INT;
a:BOOL;
b:BOOL;
c:BOOL;
d:BOOL;
END_VAR

BEGIN
REPEAT
i:=0;
i:=i+1;
IF a THEN
b:=true;
ELSE
IF b THEN
IF c THEN
d:=true;
END_IF;
ELSE
d:=false;
EXIT;
END_IF;

IF d THEN
a:=true;
END_IF;
END_IF;
UNTIL i>20
END_REPEAT;

END_FUNCTION

but it's not correct.
Help me ,please