n, M, P, Q = gets.split.map(&:to_i)

month = 1
month_count = 0
loop do
  month_count += 1
  n -= M

  if P + Q > 12
    n -= M if month.between?(P, 12) || month.between?(1, (P + Q - 1) % 12)
  elsif month.between?(P, P + Q - 1)
    n -= M
  end

  break if n <= 0

  month += 1
  month = 1 if month > 12
end

puts month_count