A, B, C, D = gets.split.map(&:to_i)

dist1 = Rational((C - A).abs + (D - B).abs, 3).ceil
dist2 = Rational((C - A).abs, 3).ceil + 1
dist3 = Rational((D - B).abs, 3).ceil + 1
dist4 = 2

puts [dist1, dist2, dist3, dist4].min