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];
   String ans = "YES"; 
   for(int i=0;i<N;i++) 
   {
     a[i] = sc.nextInt();
   }
   Arrays.sort(a);
   int tmp = a[0];
   for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   }
   System.out.print(ans);
 }
} 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];
   String ans = "YES"; 
   for(int i=0;i<N;i++) 
   {
     a[i] = sc.nextInt();
   }
   Arrays.sort(a);
   int tmp = a[0];
   for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   }
   System.out.print(ans);
 }
} Main public static void main(String[] args){
   Scanner sc = new Scanner(System.in);
   int N = sc.nextInt();
   int[] a = new int[N];
   String ans = "YES"; 
   for(int i=0;i<N;i++) 
   {
     a[i] = sc.nextInt();
   }
   Arrays.sort(a);
   int tmp = a[0];
   for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   }
   System.out.print(ans);
 } main {
   Scanner sc = new Scanner(System.in);
   int N = sc.nextInt();
   int[] a = new int[N];
   String ans = "YES"; 
   for(int i=0;i<N;i++) 
   {
     a[i] = sc.nextInt();
   }
   Arrays.sort(a);
   int tmp = a[0];
   for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   }
   System.out.print(ans);
 } 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 String ans = "YES"; ans "YES" 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 int tmp = a[0]; tmp a[0] a 0 for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   } int i =1; int i =1; i 1 i<N i N i++ i++ i {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   } {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   } if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     } a[i] == tmp a[i] a i tmp {
       ans = "NO";
       break;
     } ans = "NO" ans "NO" break; tmp = a[i] tmp a[i] a i System.out.print(ans) System.out.print System.out System System.out ans 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];
   String ans = "YES"; 
   for(int i=0;i<N;i++) 
   {
     a[i] = sc.nextInt();
   }
   Arrays.sort(a);
   int tmp = a[0];
   for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   }
   System.out.print(ans);
 }
} public class Main{
 public static void main(String[] args){
   Scanner sc = new Scanner(System.in);
   int N = sc.nextInt();
   int[] a = new int[N];
   String ans = "YES"; 
   for(int i=0;i<N;i++) 
   {
     a[i] = sc.nextInt();
   }
   Arrays.sort(a);
   int tmp = a[0];
   for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   }
   System.out.print(ans);
 }
} 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];
   String ans = "YES"; 
   for(int i=0;i<N;i++) 
   {
     a[i] = sc.nextInt();
   }
   Arrays.sort(a);
   int tmp = a[0];
   for(int i =1;i<N;i++)
   {
     if(a[i] == tmp) 
     {
       ans = "NO";
       break;
     }
     tmp = a[i];
   }
   System.out.print(ans);
 }
}