#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n; cin >> n;
    vector<int>buff(n);

    for (int i = 0; i < n; ++i) cin >> buff[i];

    int ans = 0, len = 0;

    //最简单的空间换时间
    map<int, int>count;

    for (int i = 0, j = 0; i < n; ++i) {
        count[buff[i]]++;
        len++;
        while(count[buff[i]] > 1) {
            count[buff[j++]]--;
            len --;
        }
        ans = max(len, ans);
    }
    cout << ans;
    return 0;
}