Computercraft TreeChop Program

print("How many trees shall I grow?")
trees= read()
turtle.select(1)

function chopTree()
  turtle.select(3)
  repeat
    turtle.detect()
  until turtle.compare()
  turtle.select(1)
  turtle.dig()
  turtle.forward()
  while turtle.detectUp() do
    turtle.digUp()
    turtle.up()
  end
  while not(turtle.detectDown()) do
    turtle.down()
  end
  turtle.back()
end

function plantTree()

  turtle.select(1)
  turtle.place()
  turtle.select(2)
  turtle.place()
end

function dropLogs()
  turtle.turnLeft()
  turtle.turnLeft()
  for inv=3, 9 do
    turtle.select(inv)
    turtle.drop(64)
  end
  turtle.turnRight()
  turtle.turnRight()
end

for l=1, trees do
  plantTree()
  chopTree()
  dropLogs()
end