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

perm_check(A) ->
    Sorted = lists:sort(A),
    Indexed = lists:zip(lists:seq(1, length(Sorted)), Sorted),
    case lists:all(fun({I, V}) -> I =:= V end, Indexed) of
        true -> 1;
        false -> 0
    end.