#include<bits/stdc++.h>
using namespace std;
const int N=1e6+5;
int vis[N],c[N],a[N];
void dfs(int x,int &cnt){
  vis[x]=1;
  cnt++;
  if(!vis[a[x]])
  dfs(a[x],cnt);
}
int main(){
  int n;
  scanf("%d",&n);
  for(int i=1;i<=n;i++){
    scanf("%d",&a[i]);
  }
  int cnt=0;
  for(int i=1;i<=n;i++){
    if(!vis[i])dfs(i,c[++cnt]);
  }
  int ans=0,gc=-1,mul=1;
  for(int i=1;i<=cnt;i++){
    int res=0;
    while(c[i]%2==0){
      c[i]/=2;
      res++;
    }
    ans=max(ans,res);
  //  cout<<c[i]<<endl;
    if(c[i]!=1){
      if(gc==-1)gc=mul=c[i]-1;
      else {gc=gcd(gc,c[i]-1);
	mul=mul*(c[i]-1);
	mul=mul/gc;
      }
    //  cout<<gc<<' '<<mul<<endl;
    }
  }
  ans+=mul;
  printf("%d\n",ans);
}