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];
    for(int i = 0; i < n; i++) {
      a[i] = sc.nextInt();
    }
    Arrays.sort(a);
    int p = 0;
    String ans = "YES";
    for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    }
    if(p > 0) ans = "NO";
    System.out.println(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];
    for(int i = 0; i < n; i++) {
      a[i] = sc.nextInt();
    }
    Arrays.sort(a);
    int p = 0;
    String ans = "YES";
    for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    }
    if(p > 0) ans = "NO";
    System.out.println(ans);
  }
} 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 p = 0;
    String ans = "YES";
    for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    }
    if(p > 0) ans = "NO";
    System.out.println(ans);
  } 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 p = 0;
    String ans = "YES";
    for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    }
    if(p > 0) ans = "NO";
    System.out.println(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 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 p = 0; p 0 String ans = "YES"; ans "YES" for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    } 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]) p++;
    } {
      if(a[i] == a[i + 1]) p++;
    } if(a[i] == a[i + 1]) p++; a[i] == a[i + 1] a[i] a i a[i + 1] a i + 1 i 1 p++ p if(p > 0) ans = "NO"; p > 0 p 0 ans = "NO" ans "NO" System.out.println(ans) System.out.println 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];
    for(int i = 0; i < n; i++) {
      a[i] = sc.nextInt();
    }
    Arrays.sort(a);
    int p = 0;
    String ans = "YES";
    for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    }
    if(p > 0) ans = "NO";
    System.out.println(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];
    for(int i = 0; i < n; i++) {
      a[i] = sc.nextInt();
    }
    Arrays.sort(a);
    int p = 0;
    String ans = "YES";
    for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    }
    if(p > 0) ans = "NO";
    System.out.println(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];
    for(int i = 0; i < n; i++) {
      a[i] = sc.nextInt();
    }
    Arrays.sort(a);
    int p = 0;
    String ans = "YES";
    for(int i = 0; i < (n - 1); i++) {
      if(a[i] == a[i + 1]) p++;
    }
    if(p > 0) ans = "NO";
    System.out.println(ans);
  }
}
