#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define PI acos(-1)
#define io ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define mem(a,b) memset((a),(b),sizeof(a))
typedef long long ll;
typedef unsigned long long ull;
#define int long long

const int maxn = 1e5 + 10;
int gcd(int a,int b) {return b?gcd(b,a%b):a;}
int lcm(int a,int b) {return a/gcd(a,b)*b;}
int n, a[maxn], vis[maxn], num[maxn];

void solve() {
    cin >> n;
    int cnt = 0;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    for(int i = 1; i <= n; i++) {
        int temp = a[i];
        if(vis[temp]) continue;
        cnt++;
        while(vis[temp] == 0) {
            vis[temp] = 1;
            temp = a[temp];
            num[cnt]++;
        }
    }
    // cout << cnt << '\n';
    // for(int i = 1; i <= cnt; i++) {
    //     cout << num[i] << " ";
    // }
    sort(num + 1, num + 1 + cnt);
    if(num[cnt] >= 5) {
        int ans = 1;
        for(int i = 1; i <= cnt; i++) {
            if(num[i] <= 4) continue;
            ans = lcm(ans, num[i] - 1);
        }
        cout << ans << '\n';
    } else {
        cout << num[cnt] << '\n';
    }
}

signed main(){
    io;
    int T = 1;
    //cin >> T;
    while(T--) {
        solve();
    }
    return 0;
}