X =
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
Y =
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
X ↔ Y
Ext-GCD(11, 11) :
i
GCD
Bezout
AOdd :
AEven :
A
↔
B
ax
ay
bx
by
|A-B|
A↔B
Sx
Sy
ax ←
Sx' ay ←
Sy' A ←
A/2 ax ←
ax + Y ay ←
ay + X ax ←
ax/2 ay ←
ay/2
0
11
11
1
0
0
1
1
11
11
1
0
0
1
0
2
11
11
1
0
0
1
0
3
11
11
1
0
0
1
0
4
11
11
1
0
0
1
0
5
11
11
1
0
0
1
0
6
11
11
1
0
0
1
0
7
11
11
1
0
0
1
0
(1)(11) - (0)(11) = 11