import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int[] a = new int[n];
        
        for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        }
        
        Arrays.sort(a);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        System.out.println("YES");
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int[] a = new int[n];
        
        for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        }
        
        Arrays.sort(a);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        System.out.println("YES");
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int[] a = new int[n];
        
        for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        }
        
        Arrays.sort(a);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        System.out.println("YES");
    } main {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int[] a = new int[n];
        
        for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        }
        
        Arrays.sort(a);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        System.out.println("YES");
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] a = new int[n]; a new int[n] n for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        } int i=0; int i=0; i 0 i<n i n i++ i++ i {
            a[i] = sc.nextInt();
        } {
            a[i] = sc.nextInt();
        } a[i] = sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc Arrays.sort(a) Arrays.sort Arrays a for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        } int i=1; int i=1; i 1 i<n i n i++ i++ i {
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        } {
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        } if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            } a[i]==a[i-1] a[i] a i a[i-1] a i-1 i 1 {
                System.out.println("NO");
                return;
            } System.out.println("NO") System.out.println System.out System System.out "NO" return; System.out.println("YES") System.out.println System.out System System.out "YES" String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int[] a = new int[n];
        
        for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        }
        
        Arrays.sort(a);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        System.out.println("YES");
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int[] a = new int[n];
        
        for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        }
        
        Arrays.sort(a);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        System.out.println("YES");
    }
} Main
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        int[] a = new int[n];
        
        for(int i=0; i<n; i++){
            a[i] = sc.nextInt();
        }
        
        Arrays.sort(a);
        
        for(int i=1; i<n; i++){
            if(a[i]==a[i-1]){
                System.out.println("NO");
                return;
            }
        }
        
        
        System.out.println("YES");
    }
}
