d = input()
h = []
for i in xrange(3):
  h.append(input())

def mod_min(H):
  if H[1] != H[0] and H[1] != H[2] and min(H) == H[1]:
    print 0
    return True
  diff = abs(H[1] - min(H[0], H[2]))
  H[1] -= (diff / d + 1) * d
  if H[1] != H[0] and H[1] != H[2] and min(H) == H[1]:
    #print "min"
    print H[1]
    return True
  return False

def mod_max(H):
  if H[1] != H[0] and H[1] != H[2] and max(H) == H[1]:
    print 0
    return True
  diff = abs(H[1] - max(H[0] ,H[2]))
  H[1] += (diff / d + 1) * d
  if H[1] != H[0] and H[1] != H[2] and max(H) == H[1]:
    #print "max"
    print H[1]
    return True
  return False

def bad():
  print -1
  return True


mod_min(h[:]) or mod_max(h[:]) or bad()