comparing inputs(not int inputs) returns AttributeError: 'tuple' object has no attribute 'as_string'

[Gfdcvn]

When I run in my lang variable cart = []

variable item = usrinput()

while item != 1 then variable cart = cart + item variable item = intinput() show(cart) finish

It outputs

AttributeError: 'tuple' object has no attribute 'as_string'

What do I do?