import java.util.*;
public class Main {
    public static void main(String [] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<Integer> List = new ArrayList<>();
        boolean check = true;
        for(int i=0;i<N;i++) List.add(sc.nextInt());
        Collections.sort(List);
        for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        }
        if(check) System.out.println("YES");
        else System.out.println("NO");
    }
} import java.util.*; util.* java public class Main {
    public static void main(String [] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<Integer> List = new ArrayList<>();
        boolean check = true;
        for(int i=0;i<N;i++) List.add(sc.nextInt());
        Collections.sort(List);
        for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        }
        if(check) System.out.println("YES");
        else System.out.println("NO");
    }
} Main public static void main(String [] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<Integer> List = new ArrayList<>();
        boolean check = true;
        for(int i=0;i<N;i++) List.add(sc.nextInt());
        Collections.sort(List);
        for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        }
        if(check) System.out.println("YES");
        else System.out.println("NO");
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<Integer> List = new ArrayList<>();
        boolean check = true;
        for(int i=0;i<N;i++) List.add(sc.nextInt());
        Collections.sort(List);
        for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        }
        if(check) System.out.println("YES");
        else System.out.println("NO");
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc ArrayList<Integer> List = new ArrayList<>(); List new ArrayList<>() boolean check = true; check true for(int i=0;i<N;i++) List.add(sc.nextInt()); int i=0; int i=0; i 0 i<N i N i++ i++ i List.add(sc.nextInt()); List.add(sc.nextInt()) List.add List sc.nextInt() sc.nextInt sc Collections.sort(List) Collections.sort Collections List for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        } int i=0; int i=0; i 0 i<N-1 i N-1 N 1 i++ i++ i {
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        } {
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        } if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            } List.get(i+1)-List.get(i)==0 List.get(i+1)-List.get(i) List.get(i+1) List.get List i+1 i 1 List.get(i) List.get List i 0 {
                check = false;
                break;
            } check = false check false break; if(check) System.out.println("YES");
        else System.out.println("NO"); check System.out.println("YES") System.out.println System.out System System.out "YES" System.out.println("NO") System.out.println System.out System System.out "NO" String [] args args public class Main {
    public static void main(String [] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<Integer> List = new ArrayList<>();
        boolean check = true;
        for(int i=0;i<N;i++) List.add(sc.nextInt());
        Collections.sort(List);
        for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        }
        if(check) System.out.println("YES");
        else System.out.println("NO");
    }
} public class Main {
    public static void main(String [] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<Integer> List = new ArrayList<>();
        boolean check = true;
        for(int i=0;i<N;i++) List.add(sc.nextInt());
        Collections.sort(List);
        for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        }
        if(check) System.out.println("YES");
        else System.out.println("NO");
    }
} Main
import java.util.*;
public class Main {
    public static void main(String [] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<Integer> List = new ArrayList<>();
        boolean check = true;
        for(int i=0;i<N;i++) List.add(sc.nextInt());
        Collections.sort(List);
        for(int i=0;i<N-1;i++){
            if(List.get(i+1)-List.get(i)==0){
                check = false;
                break;
            }
        }
        if(check) System.out.println("YES");
        else System.out.println("NO");
    }
}