function Back(a)
  local x = {}
  local dmax,dmin
  local LP,GL,xLP
  local dcount = 0
  local ret = 0
  local glret = 0
  local GL = 0
  local i = 1
  local wcount = 0
  local YStat = 0
  local sharp = {}
  local DriveBy = 0
  motor(0,a,0,a+1)
  repeat
    x[1],x[2],x[3],x[4],x[5] = snabel()
    x[1] = ((x[1] - cs1) * 1000) / (ch1-cs1)
    x[2] = ((x[2] - cs2) * 1000) / (ch2-cs2)
    x[3] = ((x[3] - cs3) * 1000) / (ch3-cs3)
    x[4] = ((x[4] - cs4) * 1000) / (ch4-cs4)
    x[5] = ((x[5] - cs5) * 1000) / (ch5-cs5)
    wcount = 0
    i = 1
    repeat
      if x[i] < 600 then
        wcount = wcount + 1
      end
      i = i + 1
    until i == 6
    if wcount > 4 then
      motor(0,0,0,0)
      return
    end
  until ccheck()
  motor(0,0,0,0)
  print("Samples "..dcount)
end