<s>
The	O
Robertson	B-Algorithm
–	I-Algorithm
Webb	I-Algorithm
rotating-knife	I-Algorithm
procedure	I-Algorithm
is	O
a	O
procedure	O
for	O
envy-free	O
cake-cutting	O
of	O
a	O
two-dimensional	O
cake	O
among	O
three	O
partners	O
.	O
</s>
<s>
Its	O
main	O
advantage	O
over	O
the	O
earlier	O
Stromquist	B-Algorithm
moving-knives	I-Algorithm
procedure	I-Algorithm
and	O
the	O
later	O
Barbanel	B-Algorithm
–	I-Algorithm
Brams	I-Algorithm
moving-knives	I-Algorithm
procedure	I-Algorithm
is	O
that	O
it	O
requires	O
only	O
a	O
single	O
moving-knife	O
.	O
</s>
<s>
The	O
rotating-knife	O
procedure	O
can	O
be	O
adapted	O
for	O
chore	B-Algorithm
division	I-Algorithm
-	O
dividing	O
a	O
cake	O
with	O
a	O
negative	O
value	O
:	O
in	O
the	O
initial	O
step	O
,	O
The	O
rightmost	O
cut	O
should	O
be	O
selected	O
,	O
instead	O
of	O
the	O
leftmost	O
cut	O
.	O
</s>
