mine

 full = false
 Fuel = true
 cposi = 0
 pposi = 0
 cposiB = 0
 pposiB = 0
 branch = false
 cposiB = 0

function forward()
  moved = turtle.forward()
  while not(moved) do
    sleep(1)
    turtle.dig()
    moved=turtle.forward()
  end
end

function checkInv()
  if turtle.getItemCount(15) ~= 0 then
     full = true
  end
end

function checkFuel()
CFuel = turtle.getFuelLevel()
   if not(branch) then
    if CFuel <= cposi then
      Fuel = false
    end
    if CFuel <= cposi + 5 then
      Fuel = false
    end
   else
     if CFuel <= cposi or CFuel <= 5+cposi or CFuel <= 42+cposi then
       Fuel =false
     end
   end
end

function checkifbranch()
  n=0
  while n < cposi  do
    n=n+4
  end
  if n == cposi and not(n==0) then
    branch = true
  end
end

function gohome()
  while cposi ~= 0 do
      forward()
      cposi = cposi-1
  end
end

function gomine()
  while cposi ~= pposi do
      forward()
      cposi = cposi+1
  end
end

function home()
  turtle.turnLeft()
  turtle.turnLeft()
  gohome()
  turtle.turnLeft()
  turtle.turnLeft()
  for i=2,15 do
    turtle.select(i)
    turtle.dropDown()
  end
     turtle.select(1)
  full = false
  if turtle.getItemCount(16) > 64 then
    turtle.select(16)
    turtle.suckUp()
    turtle.select(2)
    turtle.dropUp()
    turtle.select(1)
  end
  while turtle.getFuelLevel() < 2*pposi do
    q=turtle.getItemCount(1)
    q= q -1
    turtle.select(2)
    turtle.refuel(q)
    turtle.select(1)
    print("refueling...")
    sleep(15)
  end
  Fuel = true
  gomine()
end

function ifhomeL()
   checkInv()
   if full then
     turtle.turnRight()
     turtle.turnRight()
     while cposiB ~= 0 do
       forward()
       cposiB = cposiB - 1
     end
     turtle.turnLeft()
     home()
     turtle.turnLeft()
     while cposiB ~= pposiB do
       forward()
       cposiB = cposiB + 1
     end
  end
end

function ifhomeR()
   checkInv()
   if full then
     turtle.turnRight()
     turtle.turnRight()
     while cposiB ~= 0 do
       forward()
       cposiB = cposiB - 1
     end
     turtle.turnRight()
     home()
     turtle.turnRight()
     while cposiB ~= pposiB do
       forward()
       cposiB = cposiB + 1
     end
  end
end

function gobranchLeft()
  pposiB = 0
  turtle.turnLeft()
  while cposiB ~= 21 do
    pposiB = pposiB + 1
    cposiB = cposiB + 1
    forward()
    ifhomeL()
    turtle.digUp()
    ifhomeL()
    turtle.digDown()
    ifhomeL()
  end
  turtle.turnLeft()
  turtle.turnLeft()
  while cposiB ~= 0 do
       forward()
if cposiB == 7 or cposiB== 14 or cposiB== 20 then
        turtle.select(16)
        turtle.placeDown()
        turtle.select(1)
    end
       cposiB = cposiB - 1
  end
  pposiB= 0
turtle.turnLeft()
end


function gobranchRight()
  pposiB = 0
  turtle.turnRight()
  while cposiB ~= 21 do
    pposiB = pposiB + 1
    cposiB = cposiB + 1
    forward()
    ifhomeR()
    turtle.digUp()
    ifhomeR()
    turtle.digDown()
    ifhomeR()
  end
  turtle.turnLeft()
  turtle.turnLeft()
  while cposiB ~= 0 do
       forward()
    if cposiB == 7 or cposiB== 14 or cposiB== 20 then
        turtle.select(16)
        turtle.placeDown()
        turtle.select(1)
    end
       cposiB = cposiB - 1
  end
  pposiB= 0
  turtle.turnRight()
end

function mineM()
turtle.select(1)
checkInv()
  checkifbranch()
  checkFuel()
  if full == true or Fuel==false then
    home()
  end
  if branch then
    gobranchLeft()
    checkFuel()
    checkInv()
    if not(Fuel) or full then
      home()
    end
    gobranchRight()
    branch=false
t=0
 while t < cposi  do
    t=t+8
  end
  if t == cposi and not(t==0) then
    turtle.select(16)
    turtle.placeDown()
    turtle.select(1)
  end

    checkFuel()
    checkInv()
    if not(Fuel) or full then
      home()
    end
  end
  forward()
  cposi= cposi+1
  pposi= pposi+1
  checkInv()
  if full then
    home()
  end
  turtle.digUp()
  checkInv()
  if full then
    home()
  end
  turtle.digDown()
  checkInv()
  if full then
    home()
  end
  turtle.turnLeft()
  forward()
  checkInv()
  if full then
    turtle.turnRight()
    turtle.turnRight()
    forward()
    turtle.turnLeft()
    home()
    turtle.turnLeft()
    forward()
  end
  turtle.digDown()
    checkInv()
  if full then
    turtle.turnRight()
    turtle.turnRight()
    forward()
    turtle.turnLeft()
    home()
    turtle.turnLeft()
    forward()
 end
   turtle.digUp()
    checkInv()
  if full then
    turtle.turnRight()
    turtle.turnRight()
    forward()
    turtle.turnLeft()
    home()
    turtle.turnLeft()
    forward()
 end
    turtle.turnRight()
    turtle.turnRight()
    forward()
forward()
  if full then
    turtle.turnRight()
    turtle.turnRight()
    forward()
    turtle.turnRight()
    home()
    turtle.turnRight()
    forward()
 end
turtle.digUp()
    checkInv()
  if full then
    turtle.turnRight()
    turtle.turnRight()
    forward()
    turtle.turnRight()
    home()
    turtle.turnRight()
    forward()
 end
turtle.digDown()
    checkInv()
  if full then
    turtle.turnRight()
    turtle.turnRight()
    forward()
    turtle.turnRight()
    home()
    turtle.turnRight()
    forward()
 end
    turtle.turnRight()
    turtle.turnRight()
    forward()
    turtle.turnRight()
end

tArgs={...}
q = tArgs[1]

 target= q*4

while pposi~= target do
mineM()
end