#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 50;
int a[N];
int main()
{
    int n;
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
        scanf("%d", a + i);
    map<int, pair<int, int>> M;
    for (int i = 0; i < n; i++)
    {
        if (M.count(a[i]))
            M[a[i]].second = i;
        else
            M[a[i]] = make_pair(i, i);
    }
    int ans = 0;
    set<int> S;
    for (int i = 0; i < n; i++) S.insert(M[a[i]].second);
    for (int i = 0; i < n; i++)
    {
        S.erase(M[a[i]].second);
        ans = max(ans, *S.rbegin() - i);
        S.insert(M[a[i]].second);
    }
    printf("%d", ans);
    return 0;
}