import strutils

const INF = int(1e9) + 100

var
  d  = stdin.readLine.parseInt
  h1 = stdin.readLine.parseInt
  h2 = stdin.readLine.parseInt
  h3 = stdin.readLine.parseInt

proc bye(x: int) = echo(x); quit 0

proc ok(x, y, z: int): bool =
  var
    ok1 = x > y and y < z
    ok2 = x < y and y > z
  result = x != z and (ok1 or ok2)

proc count(my, your, d: int): int =
  if your == 0: return INF
  if my < your: return 0
  result = (my - your + d) div d

proc cut(my, d, times: int): int =
  result = max(0, my-d*times)

if ok(h1, h2, h3):
  bye(0)
if d == 0:
  bye(-1)

var x, y, z, p, q: int

var r1 = 0
x = h1
y = h2
z = h3
if x == z:
  x = cut(x, d, 1)
  r1 += 1
p = count(x, y, d)
r1 += p
x = cut(x, d, p)
q = count(z, y, d)
r1 += q
z = cut(z, d, q)
if not ok(x, y, z):
  r1 = INF

var r2 = 0
x = h1
y = h2
z = h3
if x == z:
  x = cut(x, d, 1)
  r2 += 1
p = count(y, x, d)
r2 += p
y = cut(y, d, p)
q = count(y, z, d)
r2 += q
y = cut(y, d, q)
if not ok(x, y, z):
  r2 = INF

var res = min(r1, r2)
if res >= INF: res = -1
echo res