program officer;
var
  i:longint;
  n,t,max,min:int64;
  sz,ans:array[1..10000]of int64;
function gcd(a,b:int64):int64;
begin
  if a mod b=0 then gcd:=b else gcd:=gcd(b,a mod b);
end;
begin
  assign(input,'officer.in');
  assign(output,'officer.out');
  reset(input);
  rewrite(output);
  readln(n);
  for i:=1 to n do
    readln(sz[i]);
  for i:=1 to n do
  begin
    ans[i]:=1;
    t:=sz[i];
    while t<>i do
    begin
      t:=sz[t];
      ans[i]:=ans[i]+1;
    end;
  end;
  max:=ans[1];
  for i:=2 to n do
  begin
    if ans[i]>=max then max:=gcd(ans[i],max) else max:=gcd(max,ans[i]);
  end;
  min:=max;
  for i:=1 to n do
    min:=min*(ans[i] div max);
  writeln(min);
  close(input);
  close(output);
end.