import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        boolean han = true;
        
        for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        }
        
        if(han) {
            System.out.println("YES");
        }else {
            System.out.println("NO");
        }
        
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        boolean han = true;
        
        for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        }
        
        if(han) {
            System.out.println("YES");
        }else {
            System.out.println("NO");
        }
        
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        boolean han = true;
        
        for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        }
        
        if(han) {
            System.out.println("YES");
        }else {
            System.out.println("NO");
        }
        
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        boolean han = true;
        
        for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        }
        
        if(han) {
            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 Map<Integer, Integer> map = new HashMap<>(); map new HashMap<>() boolean han = true; han true for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        } {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        } int s = sc.nextInt(); s sc.nextInt() sc.nextInt sc if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            } map.containsKey(s) map.containsKey map s {
                han = false;
                break;
            } han = false han false break; {
                map.put(s, 1);
            } map.put(s, 1) map.put map s 1 if(han) {
            System.out.println("YES");
        }else {
            System.out.println("NO");
        } han {
            System.out.println("YES");
        } System.out.println("YES") System.out.println System.out System System.out "YES" {
            System.out.println("NO");
        } 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) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        boolean han = true;
        
        for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        }
        
        if(han) {
            System.out.println("YES");
        }else {
            System.out.println("NO");
        }
        
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        boolean han = true;
        
        for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        }
        
        if(han) {
            System.out.println("YES");
        }else {
            System.out.println("NO");
        }
        
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        boolean han = true;
        
        for(int i = 0; i < N; i++) {
            int s = sc.nextInt();
            if(map.containsKey(s)) {
                han = false;
                break;
            }else {
                map.put(s, 1);
            }
        }
        
        if(han) {
            System.out.println("YES");
        }else {
            System.out.println("NO");
        }
        
    }
}
