# t39
# C4B:    1.33 + 0.67 |[z,y]| ticks
# eocimp: [1 | ⊤] + [y + -z | y + -z ≥ 0]

def countUpDown():
  var y, z, o, upDown

  o = 0
  upDown = 0

  while o = 0:
    tick 1
    if upDown = 0:
      if y > z:
        y = y - 1
        upDown = 1
      else:
        o = 1
    else:
      if z + 1 < y:
        z = z + 2
        upDown = 0
      else:
        o = 1

# def countUpDown():
#   var x, y, a
#
#   while 0 = 0:
#     a = x
#     if a > y:
#       tick 1
#       a = a - 1
#     else:
#       skip
#
#     x = a
#
#     if a + 1 < x:
#       tick 1
#       a = a + 2
#     else:
#       skip
#
#     y = a