#include <iostream>
#include <cstdio>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

typedef vector<int> t_positions;
typedef pair<int, int> t_interval;

void solve() {
    int N;
    cin >> N;

    vector<int> A(N);
    for (int i = 0; i < N; ++i) {
        cin >> A[i];
    }

    map<int, t_positions> key_to_pos;
    for (int i = 0; i < N; ++i) {
        key_to_pos[A[i]].push_back(i);
    }

    vector<t_interval> intervals;
    map<t_interval, int> interval_to_count;
    for (map<int, t_positions>::const_iterator it = key_to_pos.begin(); it != key_to_pos.end(); ++it) {
        t_positions pos = it->second;
        sort(pos.begin(), pos.end());

        t_interval interval = make_pair(*pos.begin(), *pos.rbegin());
        intervals.push_back(interval);
        interval_to_count[interval] = pos.size();
    }

    sort(intervals.begin(), intervals.end());

    vector<int> best(intervals.size());
    for (int i = 0; i < intervals.size(); ++i) {
        const t_interval& interval = intervals[i];

        best[i] = interval_to_count[interval];
        for (int j = 0; j < i; ++j) {
            if (intervals[j].second < interval.first) {
                best[i] = max(best[i], best[j] + interval_to_count[interval]);
            }
        }
    }

    int result = *max_element(best.begin(), best.end());
    cout << result << endl;
}

int main() {
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);

    solve();

    return 0;
}