N, M, P, Q = gets.split.map(&:to_i)
month = 0
n = N
ans = 0

while n > 0
  if P - 1 <= month && month <= P + Q - 2
    n -= 2 * M
  else
    n -= M
  end

  month = (month + 1) % 12
  ans += 1
end

puts ans