#include <iostream>

long gcd(long a, long b) {
		return b == 0 ? a : gcd(b, a % b);
}

long calcLCM(long a, long b) {
	return a * b / gcd(a,b);
}

int main() {
	int n, *perm, *used;
	std::cin >> n;
	perm = new int[n];
	used = new int[n];
	long lcm = 1;
	for(int i = 0; i < n; i ++) {
		std::cin >> perm[i];
		perm[i]--;
		used[i] = 0;
	}
	int high = 0;
	while(high < n) {
		int curr = high; bool first = true;
		int clen = 0;
		while(first || curr != high) {
			first = false;
			used[curr] = 1;
			curr = perm[curr];
			clen ++;
		}
		lcm = calcLCM(lcm, clen);
		while(high < n && used[high] == 1) high++;
	}
	std::cout << lcm;
	delete[] perm;
	delete[] used;
	return 0;
}