import java.util.*;

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

class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int[] num = new int[n];
        for(int i = 0;i < n;i++){
            num[i] = sc.nextInt();
        }
        Arrays.sort(num);
        for(int i = 0;i < n-1;i++){
            if(num[i]==num[i+1]){
                System.out.println("NO");
                return;
            }
        }
        
        System.out.println("YES");
    }
}