#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 a=11,s=11,d,f,g,h,j,k,l,i,n,m;

int main(){
    int n;
    cin >> n;
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
        cin >> x >> y;
        if(a!=11 && a!=x) {k=1;}
        if(s!=11 && s!=y) {l=1;}
        a=x;s=y;
    }
    
    cout<<((k&l) ? "NO" : "YES");
    return 0;
}