import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.next());
        }
        boolean flag = false;
        Set<String> checkHash = new HashSet<String>();
        for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        }

        if (flag) {
            System.out.println("NO");
        } else {
            System.out.println("YES");
        }

    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.next());
        }
        boolean flag = false;
        Set<String> checkHash = new HashSet<String>();
        for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        }

        if (flag) {
            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();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.next());
        }
        boolean flag = false;
        Set<String> checkHash = new HashSet<String>();
        for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        }

        if (flag) {
            System.out.println("NO");
        } else {
            System.out.println("YES");
        }

    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.next());
        }
        boolean flag = false;
        Set<String> checkHash = new HashSet<String>();
        for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        }

        if (flag) {
            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 List<String> list = new ArrayList<>(); list new ArrayList<>() for (int i = 0; i < n; i++) {
            list.add(sc.next());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            list.add(sc.next());
        } {
            list.add(sc.next());
        } list.add(sc.next()) list.add list sc.next() sc.next sc boolean flag = false; flag false Set<String> checkHash = new HashSet<String>(); checkHash new HashSet<String>() for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        } String str list {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        } {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        } if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            } checkHash.contains(str) checkHash.contains checkHash str {
                flag = true;
                break;
            } flag = true flag true break; {
                checkHash.add(str);
            } checkHash.add(str) checkHash.add checkHash str if (flag) {
            System.out.println("NO");
        } else {
            System.out.println("YES");
        } flag {
            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();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.next());
        }
        boolean flag = false;
        Set<String> checkHash = new HashSet<String>();
        for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        }

        if (flag) {
            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();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.next());
        }
        boolean flag = false;
        Set<String> checkHash = new HashSet<String>();
        for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        }

        if (flag) {
            System.out.println("NO");
        } else {
            System.out.println("YES");
        }

    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.next());
        }
        boolean flag = false;
        Set<String> checkHash = new HashSet<String>();
        for(String str : list) {
            if(checkHash.contains(str)) {
                flag = true;
                break;
            } else {
                checkHash.add(str);
            }
        }

        if (flag) {
            System.out.println("NO");
        } else {
            System.out.println("YES");
        }

    }
}
