t = turtle
function moveForward()
    if t.detect() then
        t.dig()
        t.forward()
    else
        t.forward()
    end
end
function fuelTurtle(distance)
    t.refuel(distance/80)
end
function moveDistance(distance)
    while distance > 0 do
        moveForward()
        distance = distance - 1
    end
end
function distanceInput()
  num = io.read()
  num = tonumber(num)
  return num
end
function turnAround()
    t.turnLeft()
    t.turnLeft()
end
function moveUp()
    if t.detectUp() then
        t.digUp()
        t.up()
    else
        t.up()
    end
end
function main()
    distance = distanceInput()
    fuelTurtle(distance)
    moveDistance(distance)
    t.refuel(1)
    moveUp()
    turnAround()
    fuelTurtle(distance)
    moveDistance(distance)
end

main()