import java.util.*;

class Name{
	String simei;
	String name;
}

public class Main {
    public static void main(String[] args) {
    	Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		Name[] list = new Name[n];
		for(int i = 0 ; i < n ; i++){
			list[i] = new Name();
			list[i].simei = scan.next();
			list[i].name = scan.next();
		}
		boolean unuseableFlg = false;
		for(int i = 0 ; i < n ; i++){
			boolean simeiFlg = false;
			boolean nameFlg = false;
			for(int j = 0 ; j < n ; j++){
				if(i == j){
					continue;
				}
				if(!simeiFlg && list[i].simei.equals(list[j].simei)){
					simeiFlg = true;
				}
				if(!nameFlg && list[i].name.equals(list[j].name)){
					nameFlg = true;
				}
				if(simeiFlg &&nameFlg){
					unuseableFlg = true;
					break;
				}
			}
			if(unuseableFlg){
				break;
			}
		}
		if(unuseableFlg){
			System.out.println("Yes");
		}else{
			System.out.println("No");
		}
    }
}