#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


int main(){
    int n, a0;
    cin >> n;
    for(a0 = 0; a0 < n; a0++){
        int x;
        int y;
        int xprev, yprev;
        int mode;
        xprev = x; yprev = y;
        cin >> x >> y;
        if (a0 == 0) continue;
        if (a0 == 1) {
            if (x == xprev) {
                mode = 1; 
            } else if (y == yprev) { 
                mode = 2;
            } else {
                break;
            } 
            continue;
        }
        if ((mode == 1 && x != xprev) ||
            (mode == 2 && y != yprev)) {
            break;
        } 
    }
    if (a0 != n) {
        cout << "NO\n";
    } else {
        cout << "YES\n";
    }
    return 0;
}