2024.01.14

# a = int(input())# b = 0# if a <= 500:#     b = a * 70 / 100# elif 500 < a and a <= 1500:#     b = 350 + (a - 500) * 40 / 100# elif 1500 < a and a <= 4500:#     b = 750 + (a - 1500) * 15 / 100# elif 4500 < a and a <= 10000:#     b = 1200 + (a - 4500) * 5 / 100# else :#     b = 1475 + (a - 10000) * 2 / 100# print('%.0f' %b)# x = input()# s = 0# for i in range(1, len(x)):#     if x[i-1] == x[i]:#         s += 5#     else :#         s += 10# print(s + 10)# a = int(input())# sum = 0# for i in range(a):#     x, y = input().split()#     x = int(x)#     y = int(y)#     n = y % x#     sum += n# print(sum)# n = int(input())# m = int(input())## ls = []# check = 0# check_ls = []## for i in range(n):#     v = []#     for j in range(n):#         v.append(0)#     ls.append(v)## for i in range(m):#     x, y = map(int, input().split())#     ls[x-1][y-1] = 1#     ls[y-1][x-1] = 1### def f(x):#     global check#     for k in range(n):#         if ls[x][k] == 1:#             if check_ls.__contains__(x) == False or check_ls.__contains__(k) == False:#                 check += 1#                 check_ls.append(x)#                 check_ls.append(k)#                 f(k)## f(0)# print(check)# check = 1# ls = []## for i in range(7):#     s = input().split()#     v = []#     for j in range(7):#         v.append(int(s[j]))#     ls.append(v)##### def find(x, y, c):#     ls[x][y] = 0#     global check#     if x >= 1:#         if ls[x-1][y] == c:#             check += 1#             find(x-1, y, c)#     if x <= 5:#         if ls[x+1][y] == c:#             check += 1#             find(x+1, y, c)#     if y >= 1:#         if ls[x][y-1] == c:#             check += 1#             find(x, y-1, c)#     if y <= 5:#         if ls[x][y+1] == c:#             check += 1#             find(x, y+1, c)### s = 0## for i in range(7):#     for j in range(7):#         if ls[i][j] != 0:#             find(i, j, ls[i][j])#             if check >= 3:#                 s += 1#             check = 1## print(s)# A = 0## ls = []# n = int(input())# for i in range(n):#     v = []#     for j in range(n):#          v.append(100)#     ls.append(v)## xK, yK = map(int, input().split())# xK -= 1# yK -= 1# x0, y0 = map(int, input().split())# x0 -= 1# y0 -= 1## def f(x, y, cnt):#     global A#     if A == 0:#         if x !=x0 or y != y0:#             ls[x][y] = cnt#             if x >= 2 and y >= 1:#                 if ls[x-2][y-1] > cnt+1:#                     f(x-2, y-1, cnt+1)##             if x >= 1 and y >= 2:#                 if ls[x - 1][y - 2] > cnt + 1:#                     f(x - 1, y - 2, cnt+1)##             if x < n-2 and y < n-1:#                 if ls[x + 2][y + 1] > cnt + 1:#                     f(x + 2, y + 1, cnt+1)##             if x < n-1 and y < n-2:#                 if ls[x + 1][y + 2] > cnt + 1:#                     f(x + 1, y + 2, cnt+1)##             if x < n-1 and y >= 2:#                 if ls[x - 1][y - 2] > cnt + 1:#                     f(x - 1, y - 2, cnt+1)##             if x < n-2 and y >= 1:#                 if ls[x + 2][y - 1] > cnt + 1:#                     f(x + 2, y - 1, cnt+1)##             if x >= 1 and y < n-2:#                 if ls[x - 1][y + 2] > cnt + 1:#                     f(x - 1, y + 2, cnt+1)##             if x >= 2 and y < n-1:#                 if ls[x - 2][y + 1] > cnt + 1:#                     f(x - 2, y + 1, cnt+1)#         else:#             A += 1#             ls[x0][y0] = cnt#             cnt = 0#     else:#         if cnt == 0:#             for i in range(n):#                 for j in range(n):#                     ls[i][j] = 0#         elif x != x0 or y != y0 and cnt < ls[x0][y0]:#             if x >= 2 and y >= 1:#                 f(x - 2, y - 1, cnt + 1)##             if x >= 1 and y >= 2:#                 f(x - 1, y - 2, cnt + 1)##             if x < n - 2 and y < n - 1:#                 f(x + 2, y + 1, cnt + 1)##             if x < n - 1 and y < n - 2:#                 f(x + 1, y + 2, cnt + 1)##             if x < n - 1 and y >= 2:#                 f(x - 1, y - 2, cnt + 1)##             if x < n - 2 and y >= 1:#                 f(x + 2, y - 1, cnt + 1)##             if x >= 1 and y < n - 2:#                 f(x - 1, y + 2, cnt + 1)##             if x >= 2 and y < n - 1:#                 f(x - 2, y + 1, cnt + 1)#         elif x == x0 and y == y0:#             ls[x0][y0] = cnt#             cnt = 0## f(xK, yK, 0)## print(ls[x0][y0])#ls = []n = int(input())for i in range(n):    v = []    for j in range(n):         v.append(668)    ls.append(v)xK, yK = map(int, input().split())xK -= 1yK -= 1x0, y0 = map(int, input().split())x0 -= 1y0 -= 1def f(x, y, cnt):    if x !=x0 or y != y0:        ls[x][y] = cnt        if x >= 2 and y >= 1:            if ls[x-2][y-1] > cnt+1:                f(x-2, y-1, cnt+1)        if x >= 1 and y >= 2:            if ls[x - 1][y - 2] > cnt + 1:                f(x - 1, y - 2, cnt+1)        if x < n-2 and y < n-1:            if ls[x + 2][y + 1] > cnt + 1:                f(x + 2, y + 1, cnt+1)        if x < n-1 and y < n-2:            if ls[x + 1][y + 2] > cnt + 1:                f(x + 1, y + 2, cnt+1)        if x < n-1 and y >= 2:            if ls[x + 1][y - 2] > cnt + 1:                f(x + 1, y - 2, cnt+1)        if x < n-2 and y >= 1:            if ls[x + 2][y - 1] > cnt + 1:                f(x + 2, y - 1, cnt+1)        if x >= 1 and y < n-2:            if ls[x - 1][y + 2] > cnt + 1:                f(x - 1, y + 2, cnt+1)        if x >= 2 and y < n-1:            if ls[x - 2][y + 1] > cnt + 1:                f(x - 2, y + 1, cnt+1)    else:        if ls[x0][y0] > cnt:            ls[x0][y0] = cntf(xK, yK, 0)print(ls[x0][y0])