-module(perm_missing_element).
-export([perm_missing_element/1]).

perm_missing_element(A) ->
    find_missing(lists:sort(A), 1).

find_missing([], Expected) ->
    Expected;
find_missing([V | Rest], Expected) ->
    case V =:= Expected of
        true -> find_missing(Rest, Expected + 1);
        false -> Expected
    end.