Wither

function moveForw()
    local try=1
    while not turtle.forward() do
        print("I can't go forward .. try:"..try)
        sleep(1)
        try=try+1
    end
end

function moveBack()
    local try=1
    while not turtle.back() do
        print("I can't go back .. try:"..try)
        sleep(1)
        try=try+1
    end
end

function moveUp()
    local try=1
    while not turtle.up() do
        print("I can't go up .. try:"..try)
        sleep(1)
        try=try+1
    end
end

function moveDown()
    local try=1
    while not turtle.down() do
        print("I can't go down .. try:"..try)
        sleep(1)
        try=try+1
    end
end

function turnL()
    turtle.turnLeft()
end
function turnR()
    turtle.turnRight()
end
function turn2()
    for A=1,2 do
        turnR()
    end
end


function placeForw()
    if not turtle.detect() then
        local try=1
        while not turtle.place() do
            print("I can't place forw. a block !..Try: "..try)
            try=try+1
            sleep(1)
        end
    end
end

function placeUp()
    if not turtle.detectUp() then
        local try=1
        while not turtle.placeUp() do
            print("I can't place up. a block !..Try: "..try)
            try=try+1
            sleep(1)
        end
    end
end

function placeDown()
    if not turtle.detectDown() then
        local try=1
        while not turtle.placeDown() do
             print("I can't place down. a block !..Try: "..try)
             try=try+1
             sleep(1)
        end
    end
end

function slctSkull()
    for a=1,16 do
        data=turtle.getItemDetail(a)
        if data then
            if data.name=="minecraft:skull" then
                turtle.select(a)
                break
            end
        end
    end
end

function slctSSand()
    for a=1,16 do
        data=turtle.getItemDetail(a)
        if data then
            if data.name=="minecraft:soul_sand" then
                turtle.select(a)
                break
            end
        end
    end
end

while true do

for a=1,4 do
    turtle.suckDown()
end

for a=1,16 do
    local data=turtle.getItemDetail(a)
    if data then
        if data.name=="minecraft:coal" then
            turtle.select(a)
            if turtle.getFuelLevel()<80 then
                turtle.refuel()
            else
                turtle.dropDown()
            end
        end
    end
end

moveUp()
moveUp()
moveForw()
turnL()
moveForw()
moveForw()
moveDown()
slctSSand()
placeDown()
placeForw()
moveBack()
placeForw()
moveUp()
placeDown()
moveForw()
slctSkull()
placeForw()
moveBack()
placeForw()
moveBack()
placeForw()
turnR()
moveBack()
moveDown()
moveDown()
sleep(120)

end