import java.util.Scanner;
import java.util.Arrays;

public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int[] A = new int[N];
    for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    }
    scan.close();

    Arrays.sort(A);

    for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    }
    System.out.println("YES");
  }
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays java.util public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int[] A = new int[N];
    for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    }
    scan.close();

    Arrays.sort(A);

    for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    }
    System.out.println("YES");
  }
} Main public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int[] A = new int[N];
    for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    }
    scan.close();

    Arrays.sort(A);

    for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    }
    System.out.println("YES");
  } main {
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int[] A = new int[N];
    for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    }
    scan.close();

    Arrays.sort(A);

    for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    }
    System.out.println("YES");
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int[] A = new int[N]; A new int[N] N for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    } int i=0; int i=0; i 0 i<N i N i++ i++ i {
      A[i] = scan.nextInt();
    } {
      A[i] = scan.nextInt();
    } A[i] = scan.nextInt() A[i] A i scan.nextInt() scan.nextInt scan scan.close() scan.close scan Arrays.sort(A) Arrays.sort Arrays A for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    } 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]) {
        System.out.println("NO");
        return;
      }
    } {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    } if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      } A[i] == A[i+1] A[i] A i A[i+1] A i+1 i 1 {
        System.out.println("NO");
        return;
      } System.out.println("NO") System.out.println System.out System System.out "NO" return; 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 scan = new Scanner(System.in);
    int N = scan.nextInt();
    int[] A = new int[N];
    for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    }
    scan.close();

    Arrays.sort(A);

    for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    }
    System.out.println("YES");
  }
} public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int[] A = new int[N];
    for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    }
    scan.close();

    Arrays.sort(A);

    for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    }
    System.out.println("YES");
  }
} Main
import java.util.Scanner;
import java.util.Arrays;

public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    int N = scan.nextInt();
    int[] A = new int[N];
    for(int i=0; i<N; i++) {
      A[i] = scan.nextInt();
    }
    scan.close();

    Arrays.sort(A);

    for(int i=0; i<N-1; i++) {
      if(A[i] == A[i+1]) {
        System.out.println("NO");
        return;
      }
    }
    System.out.println("YES");
  }
}