function goto( gx, gy, gz )
    if gx == nil or gy == nil or gz == nil then
        return
    end
    --defining x, y, z, f position
    cx, cy, cz = gps.locate( 2, false )
    if cf == nil then
        turtle.dig()
        repeat until turtle.forward()
        local fx, fy, fz = gps.locate( 2, false )
        if cz < fz then
            cf = 0
        elseif cx > fx then
            cf = 1
        elseif cz > fz then
            cf = 2
        elseif cx < fx then
            cf = 3
        end
        repeat until turtle.back()
    end

    while cx ~= gx or cz ~= gz do
        if cf == 0 then
            if cx < gx then
                turtle.turnLeft()
                cf = 3
            elseif cx > gx or cz > gz then
                turtle.turnRight()
                cf = 1
            end
        elseif cf == 1 and cx <= gx then
            if cz > gz or cx ~= gx then
                turtle.turnRight()
                cf = 2
            elseif cz < gz then
                turtle.turnLeft()
                cf = 0
            end
        elseif cf == 2 then
            if cx > gx then
                turtle.turnLeft()
                cf = 1
            elseif cx < gx or cz < gz then
                turtle.turnRight()
                cf = 3
            end
        elseif cf == 3 and cx >= gx then
            if cz < gz or cx ~= gx then
                turtle.turnRight()
                cf = 0
            elseif cz > gz then
                turtle.turnLeft()
                cf = 2
            end
        end
        if cf == 1 or cf == 3 then
            while cx ~= gx or not turtle.detectDown() do
                if turtle.down() then
                    cy = cy - 1
                elseif cx ~= gx then
                    while not turtle.forward() do
                        while not turtle.up() do
                            while not turtle.back() do
                                while not turtle.down() do
                                    return
                                end
                                cy = cy - 1
                            end
                            if cf == 1 then
                                cx = cx + 1
                            else
                                cx = cx - 1
                            end
                        end
                        cy = cy+1
                    end
                    if cf == 1 then
                        cx = cx - 1
                    else
                        cx = cx + 1
                    end
                end
            end
        elseif cx == gx then
            while cz ~= gz or not turtle.detectDown() do
                if turtle.down() then
                    cy = cy - 1
                elseif cz ~= gz then
                    while not turtle.forward() do
                        while not turtle.up() do
                            while not turtle.back() do
                                while not turtle.down() do
                                    return
                                end
                                cy = cy - 1
                            end
                            if cf == 0 then
                                cz = cz - 1
                            else
                                cz = cz + 1
                            end
                        end
                        cy = cy + 1
                    end
                    if cf == 0 then
                        cz = cz + 1
                    else
                        cz = cz - 1
                    end
                end
            end
        end
    end

    while cy ~= gy do
        if cy < gy then
            turtle.digUp()
            if turtle.up() then
                cy = cy + 1
            end
        else
            turtle.digDown()
            if turtle.down() then
                cy = cy - 1
            end
        end
    end
end