#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <ctime>

using namespace std;

bool solve(vector<int> &a){
	int n = a.size();
	vector<int> s(n);
	for(int i=0; i<n; i++){
		s[i] = i;
	}
	random_shuffle(s.begin(), s.end());

	vector<bool> used(n, false);
	
	bool valid = true;
	for(int i=0; i<n; i++){
		bool ok = false;
		for(int j=0; j<n; j++){
			if(i== s[j] || s[j] == a[i]) continue;
			if(used[ s[j] ]) continue;
			used[ s[j] ] = true;
			ok = true;
			break;
		}
		if(!ok) valid = false;
	}

	return valid;
}

int main(){
	srand((unsigned)time(NULL));
	
	int n;
	cin >> n;
	vector<int> a(n);
	for(int i=0; i<n; i++){
		cin >> a[i];
		a[i]--;
	}

	bool valid = false;
	for(int i=0; i<100000 && !valid; i++){
		valid |= solve(a);
	}

	cout << (valid?"Yes":"No") << endl;
	return 0;
}