import java.util.*;
public class Main{
	public static void main(String[] args){
    	Scanner sc=new Scanner(System.in);
    	int n=sc.nextInt();
    	int[] x=new int[n];
    	boolean can = true;
    	for(int i=0;i<n;i++)
    		x[i] = sc.nextInt();
    	Arrays.sort(x);
    	for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	}
    	String s = can?"YES":"NO";
    	System.out.println(s);
	}
} 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[] x=new int[n];
    	boolean can = true;
    	for(int i=0;i<n;i++)
    		x[i] = sc.nextInt();
    	Arrays.sort(x);
    	for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	}
    	String s = can?"YES":"NO";
    	System.out.println(s);
	}
} Main public static void main(String[] args){
    	Scanner sc=new Scanner(System.in);
    	int n=sc.nextInt();
    	int[] x=new int[n];
    	boolean can = true;
    	for(int i=0;i<n;i++)
    		x[i] = sc.nextInt();
    	Arrays.sort(x);
    	for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	}
    	String s = can?"YES":"NO";
    	System.out.println(s);
	} main {
    	Scanner sc=new Scanner(System.in);
    	int n=sc.nextInt();
    	int[] x=new int[n];
    	boolean can = true;
    	for(int i=0;i<n;i++)
    		x[i] = sc.nextInt();
    	Arrays.sort(x);
    	for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	}
    	String s = can?"YES":"NO";
    	System.out.println(s);
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] x=new int[n]; x new int[n] n boolean can = true; can true for(int i=0;i<n;i++)
    		x[i] = sc.nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i x[i] = sc.nextInt(); x[i] = sc.nextInt() x[i] x i sc.nextInt() sc.nextInt sc Arrays.sort(x) Arrays.sort Arrays x for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	} int i=0; int i=0; i 0 i<n-1 i n-1 n 1 i++ i++ i {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	} {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	} if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		} x[i]==x[i+1] x[i] x i x[i+1] x i+1 i 1 {
    			can = false;
    				break;
    		} can = false can false break; String s = can?"YES":"NO"; s can?"YES":"NO" can "YES" "NO" System.out.println(s) System.out.println System.out System System.out s String[] args args public class Main{
	public static void main(String[] args){
    	Scanner sc=new Scanner(System.in);
    	int n=sc.nextInt();
    	int[] x=new int[n];
    	boolean can = true;
    	for(int i=0;i<n;i++)
    		x[i] = sc.nextInt();
    	Arrays.sort(x);
    	for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	}
    	String s = can?"YES":"NO";
    	System.out.println(s);
	}
} public class Main{
	public static void main(String[] args){
    	Scanner sc=new Scanner(System.in);
    	int n=sc.nextInt();
    	int[] x=new int[n];
    	boolean can = true;
    	for(int i=0;i<n;i++)
    		x[i] = sc.nextInt();
    	Arrays.sort(x);
    	for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	}
    	String s = can?"YES":"NO";
    	System.out.println(s);
	}
} Main
import java.util.*;
public class Main{
	public static void main(String[] args){
    	Scanner sc=new Scanner(System.in);
    	int n=sc.nextInt();
    	int[] x=new int[n];
    	boolean can = true;
    	for(int i=0;i<n;i++)
    		x[i] = sc.nextInt();
    	Arrays.sort(x);
    	for(int i=0;i<n-1;i++) {
    		if(x[i]==x[i+1]) {
    			can = false;
    				break;
    		}
    	}
    	String s = can?"YES":"NO";
    	System.out.println(s);
	}
}