digD

local blocks = 0
term.write("How many blocks down? :")
blocks = read()

function digAll()
	turtle.digUp()
	turtle.dig()
	turtle.digDown()
end

function gravel()
	if turtle.detect() then
		digAll()
	end
end

function One()
	for i = 1, blocks do
		inch()
	end
end

function inch()
	digAll()
	gravel()
	turtle.down()
	turtle.dig()
	turtle.forward()
end

One()