#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int main(){
    int n; 
    bool result=1;
    int lastX=0, lastY=0;
    scanf("%d",&n);
    for(int a0 = 0; a0 < n; a0++){
        int x; 
        int y; 
        scanf("%d %d",&x,&y);
        if (a0>0){if(lastX!=x &&  lastY!=y){result =0;}}
        lastX=x;
        lastY=y;
    }
    if(result==1){printf("YES");}else printf("NO");
    return 0;
}