#include <iostream>
#include <vector>
#include <set>

void solve() {
    int n;
    std::cin >> n;

    std::vector<int> xs(n);
    for (auto& x : xs) std::cin >> x;

    std::set<int> s;
    int ans = 0, r = 0;
    for (int l = 0; l < n; ++l) {
        while (r < n && !s.count(xs[r])) {
            s.insert(xs[r++]);
        }

        ans = std::max(ans, r - l);
        s.erase(xs[l]);
    }

    std::cout << ans << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}