#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) {
  while (b) {
    int r = a % b;
    a = b;
    b = r;
  }
  return a;
}
int64_t lcm(int a, int b) { return 1LL * a * b / gcd(a, b); }
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int n;
  cin >> n;
  vector<int> next(n + 1);
  for (int i = 1; i <= n; i++) cin >> next[i];
  int64_t ans = 1;
  vector<bool> cycle(n + 1);
  for (int i = 1; i <= n; i++)
    if (!cycle[i]) {
      int node = i;
      vector<int> vis(n + 1);
      for (int j = 0; j < n + 1; j++) {
        vis[node]++;
        node = next[node];
      }
      if (vis[i] >= 2) {
        int len = 0, node = i;
        while (!cycle[node]) {
          len++;
          cycle[node] = true;
          node = next[node];
        }
        ans = lcm(ans, len);
      }
    }
  int mx = 0;
  for (int i = 1; i <= n; i++)
    if (!cycle[i]) {
      int dist = 0, node = i;
      while (!cycle[node]) {
        dist++;
        node = next[node];
      }
      mx = max(mx, dist);
    }
  int it = 1;
  while (it * ans < mx) it++;
  cout << it * ans << '\n';
  return 0;
}
