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];
        boolean test = true;
        
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        for(int i=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        }
        if(test){
            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();
        int[] a = new int[N];
        boolean test = true;
        
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        for(int i=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        }
        if(test){
            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();
        int[] a = new int[N];
        boolean test = true;
        
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        for(int i=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        }
        if(test){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] a = new int[N];
        boolean test = true;
        
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        for(int i=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        }
        if(test){
            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 int[] a = new int[N]; a new int[N] N boolean test = true; test true 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=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        } int i=0; int i=0; i 0 i<N-1 i N-1 N 1 i++ i++ i {
            if(a[i] == a[i+1]){
                test = false;
            }
        } {
            if(a[i] == a[i+1]){
                test = false;
            }
        } if(a[i] == a[i+1]){
                test = false;
            } a[i] == a[i+1] a[i] a i a[i+1] a i+1 i 1 {
                test = false;
            } test = false test false if(test){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        } test {
            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){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] a = new int[N];
        boolean test = true;
        
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        for(int i=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        }
        if(test){
            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();
        int[] a = new int[N];
        boolean test = true;
        
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        for(int i=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        }
        if(test){
            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();
        int[] a = new int[N];
        boolean test = true;
        
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        for(int i=0; i<N-1; i++){
            if(a[i] == a[i+1]){
                test = false;
            }
        }
        if(test){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
    }
}