import java.util.Arrays;
import java.util.Scanner;
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);
    int cou = 0;
    for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    }
    if(cou == 0) {
    	System.out.println("YES ");
    }else {
    	System.out.println("NO ");
    }  
      }
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner 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);
    int cou = 0;
    for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    }
    if(cou == 0) {
    	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];
   
    for(int i=0; i<n; i++) {
    	a[i] = sc.nextInt();
    	    }
    Arrays.sort(a);
    int cou = 0;
    for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    }
    if(cou == 0) {
    	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];
   
    for(int i=0; i<n; i++) {
    	a[i] = sc.nextInt();
    	    }
    Arrays.sort(a);
    int cou = 0;
    for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    }
    if(cou == 0) {
    	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 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 cou = 0; cou 0 for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    } 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]) {
    		cou++;
    	}
    } {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    } if(a[i] == a[i+1]) {
    		cou++;
    	} a[i] == a[i+1] a[i] a i a[i+1] a i+1 i 1 {
    		cou++;
    	} cou++ cou if(cou == 0) {
    	System.out.println("YES ");
    }else {
    	System.out.println("NO ");
    } cou == 0 cou 0 {
    	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];
   
    for(int i=0; i<n; i++) {
    	a[i] = sc.nextInt();
    	    }
    Arrays.sort(a);
    int cou = 0;
    for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    }
    if(cou == 0) {
    	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];
   
    for(int i=0; i<n; i++) {
    	a[i] = sc.nextInt();
    	    }
    Arrays.sort(a);
    int cou = 0;
    for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    }
    if(cou == 0) {
    	System.out.println("YES ");
    }else {
    	System.out.println("NO ");
    }  
      }
} Main
import java.util.Arrays;
import java.util.Scanner;
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);
    int cou = 0;
    for(int i=0; i<n-1; i++) {
    	if(a[i] == a[i+1]) {
    		cou++;
    	}
    }
    if(cou == 0) {
    	System.out.println("YES ");
    }else {
    	System.out.println("NO ");
    }  
      }
}
