os.loadAPI("ocs/apis/sensor")
function radius(pos)
  return math.sqrt((pos.X)^2+(pos.Z)^2)
end

local ss = sensor.wrap("top")

while true do
  local signal = true
  local me = ss.getTargets()["MrBartek21"]
  if me~=nil then
    signal = (radius(me.Position)>5)
  end
  redstone.setOutput("left",signal)
end