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];
    HashMap map = new HashMap();
    boolean flg = true;
    for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     }

     if (flg) {
         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];
    HashMap map = new HashMap();
    boolean flg = true;
    for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     }

     if (flg) {
         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];
    HashMap map = new HashMap();
    boolean flg = true;
    for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     }

     if (flg) {
         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];
    HashMap map = new HashMap();
    boolean flg = true;
    for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     }

     if (flg) {
         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 HashMap map = new HashMap(); map new HashMap() boolean flg = true; flg true for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     } int i=0; int i=0; i 0 i<n i n i++ i++ i {
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     } {
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     } a[i]=sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        } map.containsKey(a[i]) map.containsKey map a[i] a i {
            flg=false;
            break;
        } flg=false flg false break; {
            map.put(a[i],a[i]);
        } map.put(a[i],a[i]) map.put map a[i] a i a[i] a i if (flg) {
         System.out.println("YES");
     } else {
        System.out.println("NO");
     } flg {
         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];
    HashMap map = new HashMap();
    boolean flg = true;
    for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     }

     if (flg) {
         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];
    HashMap map = new HashMap();
    boolean flg = true;
    for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     }

     if (flg) {
         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];
    HashMap map = new HashMap();
    boolean flg = true;
    for (int i=0;i<n;i++){
	    a[i]=sc.nextInt();
        if (map.containsKey(a[i])) {
            flg=false;
            break;
        } else {
            map.put(a[i],a[i]);
        }
     }

     if (flg) {
         System.out.println("YES");
     } else {
        System.out.println("NO");
     }
  }
}





