#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

int N, a[1000], x;

void input()
{
    scanf("%d", &N);
    for( int i = 0; i < N; i++ )
        scanf("%d", &a[i]);

    scanf("%d", &x);
}

void solve() /// binary search
{
    sort(a, a+N);
    int left = 0, right = N-1;
    int mid = (left + right) / 2;

    bool found = false;
    while( left <= right )
    {
        if( a[mid] < x )
        {
            left = mid + 1;
        }
        else if( a[mid] > x )
        {
            right = mid - 1;
        }
        else
        {
            found = true;
            break;
        }

        mid = (left + right) / 2;
    }

    if( found )
        printf("YES\n");
    else
        printf("NO\n");
}

int main()
{
    input();
    solve();

    return 0;
}