var
  a: array[1..1000, 1..10001] of integer; c, d, e: integer;

label 1;
begin
  randomize;
  d := 1;
  Readln(c);
  for e := 1 to c do read(a[e, 10001]) {a[e,1002]:=random(c-1)+1};
  for e := 1 to c do a[e, 1] := e;
  1: inc(d);
  //for e:= 1 to c do write (a[e,1001],' ');
  for e := 1 to c do a[a[e, 10001], d] := a[e, d - 1];
  for e := 1 to c do if a[e, d] <> a[e, 1] then goto 1;
  writeln(d - 1);
end.