import java.util.*;
import java.lang.Math;
 
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);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  }
} import java.util.*; util.* java import java.lang.Math; Math java.lang 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);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  }
} 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);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  } 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);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  } 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] A i sc.nextInt() sc.nextInt sc Arrays.sort(A) Arrays.sort Arrays A boolean flg = false; flg false for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true; int i = 0; int i = 0; i 0 i + 1 < N i + 1 i 1 N i++ i++ i if (A[i] == A[i + 1]) flg = true; if (A[i] == A[i + 1]) flg = true; A[i] == A[i + 1] A[i] A i A[i + 1] A i + 1 i 1 flg = true flg true if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    } flg {
      System.out.println("NO");
    } System.out.println("NO") System.out.println System.out System System.out "NO" {
      System.out.println("YES");
    } System.out.println("YES") System.out.println System.out System System.out "YES" 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);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  }
} 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);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  }
} Main
import java.util.*;
import java.lang.Math;
 
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);
    
    boolean flg = false;
    
    for (int i = 0; i + 1 < N; i++) if (A[i] == A[i + 1]) flg = true;
    
    
    if (flg) {
      System.out.println("NO");
    } else {
      System.out.println("YES");
    }
  }
}