program ex;
var
a,b:array[1..10000] of longint;
f:array[1..10000] of boolean;
x,z,i,j,n,m:longint;

procedure init;
begin
  assign(input,'officer.in');
  assign(output,'officer.out');
  reset(input);
  rewrite(output);
  readln(n);
  for i:=1 to n do readln(a[i]);
  close(input);
  for i:=1 to 10000 do f[i]:=true;
end;

function qiu(a,b:longint):longint;
var
c,d,t:longint;
begin
  c:=a*b;
  t:=a mod b;
  while t<>0 do
  begin
    a:=0;
    a:=b;
    b:=t;
    t:=a mod b;
  end;
  qiu:=c div b
end;

begin
  init;
  x:=0;
  for i:=1 to n do
  begin
    if f[i]=true then
    begin
      j:=i;z:=1;f[j]:=false;
      while a[j]<>i do
      begin
        j:=a[j];
        f[j]:=false;
        inc(z);
      end;
    inc(x);
    b[x]:=z;
    end;
  end;
  m:=b[1];
  for i:=2 to x do
  begin
    m:=qiu(m,b[i]);
  end;
  writeln(m);
  close(output);
end.