Lua错误：＆＃39; <eof>＆＃39;预期

Question

有一个我无法摆脱的错误。当我运行脚本时，每次都会发生以下错误：

bios:14: [string "Digger"]:35: '<eof>' expected

write("X:")
x = read()
write("Y:")
y = read()
write("Z:")
z = read()
for zi=0, z, 1 do
    for xi=0, x, 1 do
        for yi=0, y, 1 do
            turtle.dig()
            turtle.forward()
        end
        if xi < x then
            if xi % 2 then
                turtle.turnLeft()
                turtle.dig()
                turtle.forward()
                turtle.turnLeft()
            else
                turtle.turnRight()
                turtle.dig()
                turtle.forward()
                turtle.turnRight()
            end
        end
    end
    if y % 2 == 1 then
        turtle.turnRight()
        for back=0, y, 1 do
            turtle.forward()
        end
        turtle.turnRight()
    end 
end

虽然我已经在互联网上发现必须有很多结果，但我发现没有错。你能告诉我出了什么问题吗？