import java.util.Scanner;

public class Yuki3009_A {


    public Yuki3009_A() {
        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();
        int[] data = new int[N];
        for (int i = 0; i < N; i++) {
            data[i] = scanner.nextInt();
        }
        int max = 0;
        //貪欲解
        for (int L = 0; L < data.length; L++) {
            boolean[] checked = new boolean[1000000 + 1];
            boolean allOK = true;
            for (int R = L; R < data.length; R++) {
                int c = data[R];
                if (checked[c]) {
                    max = Math.max(max, R - L);
                    allOK = false;
                    break;
                }
                checked[c] = true;
            }
            if (allOK) {
                max = Math.max(max, data.length - L);
            }

        }

        System.out.println(max);
    }

    public static void main(String[] args) {
        Yuki3009_A hoge = new Yuki3009_A();
    }
}