2 horses

start1, start2 = input().split()

x1, y1 = start1
x2, y2 = start2

x1 = ord(x1) - ord('a')
x2 = ord(x2) - ord('a')

y1 = int(y1) - 1
y2 = int(y2) - 1

visited = set()
visited.add((x1, y1, x2, y2))
q = [(x1, y1, x2, y2, 0)]

res = -1

while q:
    x1, y1, x2, y2, steps = q.pop(0)
    if x1 == x2 and y1 == y2:
        res = steps
        break
    for xp1, yp1 in [(x1-2, y1+1), (x1-2, y1-1), (x1-1, y1-2), (x1-1, y1+2),
        (x1+1, y1-2), (x1+1, y1+2), (x1+2, y1-1), (x1+2, y1+1)]:
        if 0 <= xp1 < 8 and 0 <= yp1 < 8:
            for xp2, yp2 in [(x2-2, y2+1), (x2-2, y2-1), (x2-1, y2-2), (x2-1, y2+2),
                (x2+1, y2-2), (x2+1, y2+2), (x2+2, y2-1), (x2+2, y2+1)]:
                if 0 <= xp2 < 8 and 0 <= yp2 < 8:
                    if (xp1, yp1, xp2, yp2) not in visited:
                        visited.add((xp1, yp1, xp2, yp2))
                        q.append((xp1, yp1, xp2, yp2, steps+1))

print(res)