// if extended is true, it also updates the cosequence Ua, Ub.
func euclidUpdate(A, B, Ua, Ub, q, r, s, t *Int, extended bool) {
	q, r = q.QuoRem(A, B, r)

	*A, *B, *r = *B, *r, *A

	if extended {
		// Ua, Ub = Ub, Ua - q*Ub
		t.Set(Ub)
		s.Mul(Ub, q)
		Ub.Sub(Ua, s)
		Ua.Set(t)
	}
}

// lehmerGCD sets z to the greatest common divisor of a and b,

	// A = Ua*a + Va*b
	// B = Ub*a + Vb*b
	Ua := new(Int).SetInt64(1)
	Va := new(Int)

	Ub := new(Int)
	Vb := new(Int).SetInt64(1)

	q := new(Int)
	temp := new(Int)

	r := new(Int)
	for len(B.abs) > 0 {
		q, r = q.QuoRem(A, B, r)

		A, B, r = B, r, A

		// Ua, Ub = Ub, Ua-q*Ub
		temp.Set(Ub)
		Ub.Mul(Ub, q)
		Ub.Sub(Ua, Ub)
		Ua.Set(temp)

00000190  2b 2b 24 23 77 5b 1c 3b  bd 75 5d ce 20 54 cf a1  |++$#w[.;.u]. T..|
000001a0  63 87 1d 1e 24 c4 f3 1d  1a 50 8b aa b6 14 43 ed  |c...$....P....C.|
000001b0  97 a7 75 62 f4 14 c8 52  d7 02 03 01 00 01 a3 46  |..ub...R.......F|
000001c0  30 44 30 0e 06 03 55 1d  0f 01 01 ff 04 04 03 02  |0D0...U.........|
000001d0  05 a0 30 13 06 03 55 1d  25 04 0c 30 0a 06 08 2b  |..0...U.%..0...+|

	SYS_MSYSCALL       = 37  // { int sys_msyscall(void *addr, size_t len); }
	SYS_STAT           = 38  // { int sys_stat(const char *path, struct stat *ub); }
	SYS_GETPPID        = 39  // { pid_t sys_getppid(void); }
	SYS_LSTAT          = 40  // { int sys_lstat(const char *path, struct stat *ub); }
	SYS_DUP            = 41  // { int sys_dup(int fd); }
	SYS_FSTATAT        = 42  // { int sys_fstatat(int fd, const char *path, \

	SYS_MSYSCALL       = 37  // { int sys_msyscall(void *addr, size_t len); }
	SYS_STAT           = 38  // { int sys_stat(const char *path, struct stat *ub); }
	SYS_GETPPID        = 39  // { pid_t sys_getppid(void); }
	SYS_LSTAT          = 40  // { int sys_lstat(const char *path, struct stat *ub); }
	SYS_DUP            = 41  // { int sys_dup(int fd); }
	SYS_FSTATAT        = 42  // { int sys_fstatat(int fd, const char *path, \

	SYS_SYNC           = 36  // { void sys_sync(void); }
	SYS_STAT           = 38  // { int sys_stat(const char *path, struct stat *ub); }
	SYS_GETPPID        = 39  // { pid_t sys_getppid(void); }
	SYS_LSTAT          = 40  // { int sys_lstat(const char *path, struct stat *ub); }
	SYS_DUP            = 41  // { int sys_dup(int fd); }
	SYS_FSTATAT        = 42  // { int sys_fstatat(int fd, const char *path, struct stat *buf, int flag); }

	SYS_SYNC           = 36  // { void sys_sync(void); }
	SYS_STAT           = 38  // { int sys_stat(const char *path, struct stat *ub); }
	SYS_GETPPID        = 39  // { pid_t sys_getppid(void); }
	SYS_LSTAT          = 40  // { int sys_lstat(const char *path, struct stat *ub); }
	SYS_DUP            = 41  // { int sys_dup(int fd); }
	SYS_FSTATAT        = 42  // { int sys_fstatat(int fd, const char *path, struct stat *buf, int flag); }

	SYS_SYNC           = 36  // { void sys_sync(void); }
	SYS_STAT           = 38  // { int sys_stat(const char *path, struct stat *ub); }
	SYS_GETPPID        = 39  // { pid_t sys_getppid(void); }
	SYS_LSTAT          = 40  // { int sys_lstat(const char *path, struct stat *ub); }
	SYS_DUP            = 41  // { int sys_dup(int fd); }
	SYS_FSTATAT        = 42  // { int sys_fstatat(int fd, const char *path, struct stat *buf, int flag); }

	SYS_MSYSCALL       = 37  // { int sys_msyscall(void *addr, size_t len); }
	SYS_STAT           = 38  // { int sys_stat(const char *path, struct stat *ub); }
	SYS_GETPPID        = 39  // { pid_t sys_getppid(void); }
	SYS_LSTAT          = 40  // { int sys_lstat(const char *path, struct stat *ub); }
	SYS_DUP            = 41  // { int sys_dup(int fd); }
	SYS_FSTATAT        = 42  // { int sys_fstatat(int fd, const char *path, struct stat *buf, int flag); }

	SYS_SYNC           = 36  // { void sys_sync(void); }
	SYS_STAT           = 38  // { int sys_stat(const char *path, struct stat *ub); }
	SYS_GETPPID        = 39  // { pid_t sys_getppid(void); }
	SYS_LSTAT          = 40  // { int sys_lstat(const char *path, struct stat *ub); }
	SYS_DUP            = 41  // { int sys_dup(int fd); }
	SYS_FSTATAT        = 42  // { int sys_fstatat(int fd, const char *path, struct stat *buf, int flag); }