essai

p = peripheral.wrap("back")
m = peripheral.wrap("top")
p.condenseItems()
maxS = p.getInventorySize()
print(maxS)
qty2 = 0

for i=1,maxS do

chest = p.getStackInSlot(i)
if chest then
  itemqty = chest.qty
  print(itemqty)
  qty2 = qty2 + itemqty
  print(qty2)
end

end

m.clear()
m.setCursorPos(1,3)
m.write(qty2)