class main{
    public static void main(String[] args){

        java.util.Scanner sc= new java.util.Scanner(System.in);
        
        int N=sc.nextInt();
        int Yescount=0;
    	
        String[] Getu=new String[N];
        String[] Date=new String[N];

        
        for(int i=0; i<N; i++){
            Getu[i] = sc.next();
            Date[i] = sc.next();
        }
    	
        for (int i = 0; i < N; i++) {
            for (int j = i + 1; j < N; j++) {
                if (Getu[i].equals(Getu[j]) && Date[i].equals(Date[j])) {
                    System.out.println("Yes");
                    Yescount++;
                		return;
                }
			}                    	
		}
        if (Yescount == 0) {
            System.out.println("No");
        }		
    }
}