local mmi, mma, mce = math.min, math.max, math.ceil
local d, h1, h2, h3 = io.read("*n", "*n", "*n", "*n")

local function getcount(d, min, mid, max)
  local cnt = 0
  if max <= mid then
    local midcnt = mce((mid - max + 1) / d)
    mid = mid - midcnt * d
    cnt = cnt + midcnt
  end
  if mid <= 0 then
    return -1
  end
  if mid <= min then
    local mincnt = mce((min - mid + 1) / d)
    -- min = min - mincnt * d
    cnt = cnt + mincnt
  end
  return cnt
end

if d == 0 then
  if h1 ~= h3 and (h1 - h2) * (h2 - h3) < 0 then
    print(0)
  else
    print(-1)
  end
else
  local ret = -1
  local a = getcount(d, h1, h3, h2)
  if 0 <= a then
    if ret == -1 then ret = a else ret = mmi(ret, a) end
  end
  a = getcount(d, h3, h1, h2)
  if 0 <= a then
    if ret == -1 then ret = a else ret = mmi(ret, a) end
  end
  a = getcount(d, h2, h1, h3)
  if 0 <= a then
    if ret == -1 then ret = a else ret = mmi(ret, a) end
  end
  a = getcount(d, h2, h3, h1)
  if 0 <= a then
    if ret == -1 then ret = a else ret = mmi(ret, a) end
  end
  print(ret)
end