import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Built using CHelper plug-in Actual solution is at the top
 *
 * @author Silviase
 */
public class Main {

  public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    Scanner in = new Scanner(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    CDistinctOrNot solver = new CDistinctOrNot();
    solver.solve(1, in, out);
    out.close();
  }

  static class CDistinctOrNot {

    public void solve(int testNumber, Scanner in, PrintWriter out) {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    }

  }
}
 import java.io.OutputStream; OutputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {

  public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    Scanner in = new Scanner(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    CDistinctOrNot solver = new CDistinctOrNot();
    solver.solve(1, in, out);
    out.close();
  }

  static class CDistinctOrNot {

    public void solve(int testNumber, Scanner in, PrintWriter out) {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    }

  }
} Main public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    Scanner in = new Scanner(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    CDistinctOrNot solver = new CDistinctOrNot();
    solver.solve(1, in, out);
    out.close();
  } main {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    Scanner in = new Scanner(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    CDistinctOrNot solver = new CDistinctOrNot();
    solver.solve(1, in, out);
    out.close();
  } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out Scanner in = new Scanner(inputStream); in new Scanner(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) CDistinctOrNot solver = new CDistinctOrNot(); solver new CDistinctOrNot() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class CDistinctOrNot {

    public void solve(int testNumber, Scanner in, PrintWriter out) {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    }

  } CDistinctOrNot public void solve(int testNumber, Scanner in, PrintWriter out) {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    } solve {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    } int n = in.nextInt(); n in.nextInt() in.nextInt in int[] a = new int[n]; a new int[n] n boolean f = true; f true for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        a[i] = in.nextInt();
      } {
        a[i] = in.nextInt();
      } a[i] = in.nextInt() a[i] a i in.nextInt() in.nextInt in Arrays.sort(a) Arrays.sort Arrays a for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      } int i = 0; int i = 0; i 0 i < n - 1 i n - 1 n 1 i++ i++ i {
        f = f && !(a[i] == a[i + 1]);
      } {
        f = f && !(a[i] == a[i + 1]);
      } f = f && !(a[i] == a[i + 1]) f f && !(a[i] == a[i + 1]) f !(a[i] == a[i + 1]) (a[i] == a[i + 1]) a[i] a i a[i + 1] a i + 1 i 1 out.println(f ? "YES" : "NO") out.println out f ? "YES" : "NO" f "YES" "NO" int testNumber testNumber Scanner in in PrintWriter out out public class Main {

  public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    Scanner in = new Scanner(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    CDistinctOrNot solver = new CDistinctOrNot();
    solver.solve(1, in, out);
    out.close();
  }

  static class CDistinctOrNot {

    public void solve(int testNumber, Scanner in, PrintWriter out) {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    }

  }
} public class Main {

  public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    Scanner in = new Scanner(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    CDistinctOrNot solver = new CDistinctOrNot();
    solver.solve(1, in, out);
    out.close();
  }

  static class CDistinctOrNot {

    public void solve(int testNumber, Scanner in, PrintWriter out) {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    }

  }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Built using CHelper plug-in Actual solution is at the top
 *
 * @author Silviase
 */
public class Main {

  public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    Scanner in = new Scanner(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    CDistinctOrNot solver = new CDistinctOrNot();
    solver.solve(1, in, out);
    out.close();
  }

  static class CDistinctOrNot {

    public void solve(int testNumber, Scanner in, PrintWriter out) {
      int n = in.nextInt();
      int[] a = new int[n];
      boolean f = true;
      for (int i = 0; i < n; i++) {
        a[i] = in.nextInt();
      }
      Arrays.sort(a);
      for (int i = 0; i < n - 1; i++) {
        f = f && !(a[i] == a[i + 1]);
      }
      out.println(f ? "YES" : "NO");
    }

  }
}

