#include <iostream>
#include <map>
using namespace std;

class ducks {
public:
	int *duckStart;
	int *duckEnd;
	int *data;
	int rounds;
	
	ducks(int*data, int size) : data(data) {
		duckStart = data;
		duckEnd = duckStart + size;
		rounds = 0;
	}

	void count() {
			int *lp = duckStart;
			int *rp = duckEnd - 1;
				
		while (duckEnd - duckStart > 1 && rp >= duckStart && lp < duckEnd) {
			map<int, int*> lpos;
			map<int, int*> rpos;
			lp = duckStart;
			rp = duckEnd - 1;
			while (rp >= duckStart && lp < duckEnd) {
				if (lp >= rp) {
					ducks dl(duckStart, lp - duckStart);
					ducks dr(rp, lp - duckStart);
					dl.count(); dr.count();
					rounds += dl.rounds > dr.rounds ? dl.rounds : dr.rounds; return;
				}
				
				if (rpos.find(*lp) == rpos.end()) {
					if (lpos.find(*lp) == lpos.end()) {
						int val = *lp;
						lpos.emplace(val, lp);
//cout << "found left " << val << endl;
					}
				} else {
					rounds++;
					duckStart = lp + 1;
					duckEnd = rpos.find(*lp)->second - 1;
					break;
				}
				if (lpos.find(*rp) == lpos.end()) {
					if (rpos.find(*rp) == rpos.end()) {
						int val = *rp;
						rpos.emplace(val, rp);
//cout << "found from right" << val << endl;
					}
				} else {
					rounds++;
					duckEnd = rp;
					duckStart = lpos.find(*rp)->second + 1;
					break;
				}
				lp++;
				rp--;
			}
		}
	}
};

int main() {
	ios::sync_with_stdio(false);
	int count;
	while (cin >> count) {
		int data[count];
		for (int i = 0; i < count; i++) cin >> data[i];
		ducks d(data, count);
		
		d.count();
		cout << d.rounds << '\n';
	}
	return 0;
}