#include <iostream>
#include <algorithm>
#include <cstdio>


const int N = 111;
int n, count[N], g[N][N], left[N], right[N], max_value, ans, f[N];


void input() {
    std::cin >> n;
    for (int i = 1; i <= n; ++i) {
        int x;
        std::cin >> x;
        right[x] = i;
        if (!left[x]) {
            left[x] = i;
        }
        ++count[x];
        max_value = std::max(max_value, x);
    }
}


void build_graph() {
    for (int i = 1; i <= max_value; ++i) {
        for (int j = 1; j <= max_value; ++j) {
            if (count[i] && count[j] && right[i] < left[j]) {
                g[i][j] = 1;
            }
        }
    }
}


int calc(int v) {
    if (f[v]) {
        return f[v];
    }
    f[v] = count[v];
    for (int next = 1; next <= max_value; ++next) {
        if (g[v][next]) {
            f[v] = std::max(f[v], count[v] + calc(next));
        }
    }
    return f[v];
}


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

    input();
    build_graph();
    for (int i = 1; i <= max_value; ++i) {
        ans = std::max(ans, calc(i));
    }
    std::cout << ans << std::endl;
    return 0;
}