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

const int nmax = 15;

int n;
pair<int, int> p[nmax];

int main()
{
    scanf("%i", &n);
    for (int i = 1; i <= n; ++ i)
        scanf("%i %i", &p[i].first, &p[i].second);

    sort(p + 1, p + n + 1);

    if (p[1].first == p[n].first) return 0 * printf("YES");

    for (int i = 1; i <= n; ++ i)
        swap(p[i].first, p[i].second);

    sort(p + 1, p + n + 1);

    if (p[1].first == p[n].first) return 0 * printf("YES");

    printf("NO");
}