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(15, 14) :
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
15
14
1
0
0
1
1
14
↔
15
0
1
1
0
1
7
14
16
7
8
2
7
↔
15
7
8
1
0
8
1
8
8
8
8
4
Even
Even
4
4
3
4
7
4
4
7
8
3
2
Even
Even
2
2
4
2
7
2
2
7
8
5
1
Even
Even
1
1
5
1
7
1
1
7
8
6
1
8
9
8
9
3
22
24
11
12
6
3
↔
1
11
12
1
1
2
0
12
13
12
13
1
26
28
13
14
7
1
1
1
1
13
14
0
(1)(15) - (1)(14) = 1