#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;
    int x;
    int y;
    cin >> n;
    cin >> x >> y;
    bool v;
    if(!x) v = 1;
    else v = 0;
    for(int a0 = 1; a0 < n; a0++){
        cin >> x >> y;
        if(v) {if(x) { cout<< "NO"; return 0;}}
        if(!v) {if(y) { cout<<"NO"; return 0;}}
    }
    cout<<"YES";
    return 0;
}