#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 5e4 + 10;
const int M = 1e6 + 10;

int n, k, pre[M];
int id = -1;

int main()
{
    scanf("%d%d", &n, &k);

    for (int i = 1; i <= n; i ++)
    {
        int x;
        scanf("%d", &x);
        if (pre[x] && pre[x] + k >= i) 
            id = max(id, x);
        pre[x] = i;
    }

    printf("%d", id);

    return 0;
}