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(2, 7) :
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
2
7
1
0
0
1
1
2
7
1
0
0
1
5
1
8
2
4
1
2
1
7
4
1
0
1
6
1
4
2
4
2
3
Even
Even
2
1
3
3
↔
1
2
1
4
1
2
0
6
2
6
2
1
Even
Even
3
1
4
1
↔
1
3
1
4
1
0
5
1
↔
1
3
1
4
1
0
6
1
↔
1
3
1
4
1
0
7
1
1
4
1
3
1
0
(4)(2) - (1)(7) = 1