var n = Int(readLine()!)!
var arr = [[Int]]()
for _ in (0..<n) {
    var tmp = readLine()!.characters.split(" ").map{Int(String($0))!}
    arr.append(tmp)
}

var allInRow = true, allInCol = true
for i in (0..<arr.count-1) {
    var x = arr[i][0]
    var y = arr[i][1]
    var x1 = arr[i+1][0]
    var y1 = arr[i+1][1]
    
    if x == x1 {
        continue
    } else {
        allInRow = false
    }
    
    if y == y1 {
        continue
    } else {
        allInCol = false
    }
}

allInRow || allInCol ? print("YES") : print("NO")