import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<String> A = new ArrayList<String>();
        int i;
        String f, s;
        for (i = 0; i < N; i++) {
            A.add(sc.next());
        }
        Collections.sort(A);
        for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        }
        System.out.println("YES");
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<String> A = new ArrayList<String>();
        int i;
        String f, s;
        for (i = 0; i < N; i++) {
            A.add(sc.next());
        }
        Collections.sort(A);
        for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        }
        System.out.println("YES");
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<String> A = new ArrayList<String>();
        int i;
        String f, s;
        for (i = 0; i < N; i++) {
            A.add(sc.next());
        }
        Collections.sort(A);
        for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        }
        System.out.println("YES");
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<String> A = new ArrayList<String>();
        int i;
        String f, s;
        for (i = 0; i < N; i++) {
            A.add(sc.next());
        }
        Collections.sort(A);
        for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        }
        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 ArrayList<String> A = new ArrayList<String>(); A new ArrayList<String>() int i; i String f f s; s for (i = 0; i < N; i++) {
            A.add(sc.next());
        } i = 0; i = 0 i 0 i < N i N i++ i++ i {
            A.add(sc.next());
        } {
            A.add(sc.next());
        } A.add(sc.next()) A.add A sc.next() sc.next sc Collections.sort(A) Collections.sort Collections A for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        } i = 0; i = 0 i 0 i < N-1 i N-1 N 1 i++ i++ i {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        } {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        } f = A.get(i) f A.get(i) A.get A i s = A.get(i+1) s A.get(i+1) A.get A i+1 i 1 if (f.equals(s)) {
                System.out.println("NO");
                return;
            } f.equals(s) f.equals f s {
                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) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<String> A = new ArrayList<String>();
        int i;
        String f, s;
        for (i = 0; i < N; i++) {
            A.add(sc.next());
        }
        Collections.sort(A);
        for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        }
        System.out.println("YES");
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<String> A = new ArrayList<String>();
        int i;
        String f, s;
        for (i = 0; i < N; i++) {
            A.add(sc.next());
        }
        Collections.sort(A);
        for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        }
        System.out.println("YES");
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        ArrayList<String> A = new ArrayList<String>();
        int i;
        String f, s;
        for (i = 0; i < N; i++) {
            A.add(sc.next());
        }
        Collections.sort(A);
        for (i = 0; i < N-1; i++) {
            f = A.get(i);
            s = A.get(i+1);
            if (f.equals(s)) {
                System.out.println("NO");
                return;
            }
        }
        System.out.println("YES");
    }
}
