import java.awt.Point;
import java.io.*;
import java.util.*;
import java.math.BigInteger;

public class Main {
    static class Solver {
        MyReader mr = new MyReader();

        public void solve() {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        }
    }

    public static void main(String[] args) {
        new Solver().solve();
    }

    static class MyReader {
        BufferedReader br;
        StringTokenizer st;

        MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        }

        Integer[] nextIntArray(int n) {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        }

        Long[] nextLongArray(int n) {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        }

        String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        }
    }

    static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }

}

 import java.awt.Point; Point java.awt import java.io.*; io.* java import java.util.*; util.* java import java.math.BigInteger; BigInteger java.math public class Main {
    static class Solver {
        MyReader mr = new MyReader();

        public void solve() {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        }
    }

    public static void main(String[] args) {
        new Solver().solve();
    }

    static class MyReader {
        BufferedReader br;
        StringTokenizer st;

        MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        }

        Integer[] nextIntArray(int n) {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        }

        Long[] nextLongArray(int n) {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        }

        String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        }
    }

    static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }

} Main public static void main(String[] args) {
        new Solver().solve();
    } main {
        new Solver().solve();
    } new Solver().solve() new Solver().solve new Solver() String[] args args static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    } swap {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    } int tmp = arr[i]; tmp arr[i] arr i arr[i] = arr[j] arr[i] arr i arr[j] arr j arr[j] = tmp arr[j] arr j tmp int[] arr arr int i i int j j static class Solver {
        MyReader mr = new MyReader();

        public void solve() {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        }
    } Solver MyReader mr = new MyReader(); mr new MyReader() public void solve() {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        } solve {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        } int n = mr.nextInt(); n mr.nextInt() mr.nextInt mr Set<Integer> set = new HashSet<>(); set new HashSet<>() for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            } {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            } int x=  mr.nextInt(); x mr.nextInt() mr.nextInt mr if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                } set.contains(x) set.contains set x {
                    System.out.println("NO");
                    return;
                } System.out.println("NO") System.out.println System.out System System.out "NO" return; {
                    set.add(x);
                } set.add(x) set.add set x System.out.println("YES") System.out.println System.out System System.out "YES" static class MyReader {
        BufferedReader br;
        StringTokenizer st;

        MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        }

        Integer[] nextIntArray(int n) {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        }

        Long[] nextLongArray(int n) {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        }

        String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        }
    } MyReader BufferedReader br; br StringTokenizer st; st MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        } MyReader {
            br = new BufferedReader(new InputStreamReader(System.in));
        } br = new BufferedReader(new InputStreamReader(System.in)) br new BufferedReader(new InputStreamReader(System.in)) String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        } next {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        } while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                } catch (Exception e) {
                    e.printStackTrace();
                } Exception e {
                    e.printStackTrace();
                } e.printStackTrace() e.printStackTrace e {
                    st = new StringTokenizer(br.readLine());
                } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() {
            return Integer.parseInt(next());
        } nextInt {
            return Integer.parseInt(next());
        } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nextLong() {
            return Long.parseLong(next());
        } nextLong {
            return Long.parseLong(next());
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble() {
            return Double.parseDouble(next());
        } nextDouble {
            return Double.parseDouble(next());
        } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine() {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        } nextLine {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        } String res = ""; res "" try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } IOException e {
                e.printStackTrace();
            } e.printStackTrace() e.printStackTrace e {
                res = br.readLine();
            } res = br.readLine() res br.readLine() br.readLine br return res; res Integer[] nextIntArray(int n) {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        } nextIntArray {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        } Integer[] arr = new Integer[n]; arr new Integer[n] n for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                arr[i] = nextInt();
            } {
                arr[i] = nextInt();
            } arr[i] = nextInt() arr[i] arr i nextInt() nextInt return arr; arr int n n Long[] nextLongArray(int n) {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        } nextLongArray {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        } Long[] arr = new Long[n]; arr new Long[n] n for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                arr[i] = nextLong();
            } {
                arr[i] = nextLong();
            } arr[i] = nextLong() arr[i] arr i nextLong() nextLong return arr; arr int n n String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        } nextStringArray {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        } String[] arr = new String[n]; arr new String[n] n for (int i = 0; i < n; i++) {
                arr[i] = next();
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                arr[i] = next();
            } {
                arr[i] = next();
            } arr[i] = next() arr[i] arr i next() next return arr; arr int n n public class Main {
    static class Solver {
        MyReader mr = new MyReader();

        public void solve() {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        }
    }

    public static void main(String[] args) {
        new Solver().solve();
    }

    static class MyReader {
        BufferedReader br;
        StringTokenizer st;

        MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        }

        Integer[] nextIntArray(int n) {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        }

        Long[] nextLongArray(int n) {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        }

        String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        }
    }

    static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }

} public class Main {
    static class Solver {
        MyReader mr = new MyReader();

        public void solve() {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        }
    }

    public static void main(String[] args) {
        new Solver().solve();
    }

    static class MyReader {
        BufferedReader br;
        StringTokenizer st;

        MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        }

        Integer[] nextIntArray(int n) {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        }

        Long[] nextLongArray(int n) {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        }

        String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        }
    }

    static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }

} Main
import java.awt.Point;
import java.io.*;
import java.util.*;
import java.math.BigInteger;

public class Main {
    static class Solver {
        MyReader mr = new MyReader();

        public void solve() {
            int n = mr.nextInt();
            Set<Integer> set = new HashSet<>();
            for (int i = 0; i < n; i++) {
                int x=  mr.nextInt();
                if(set.contains(x)){
                    System.out.println("NO");
                    return;
                }
                else{
                    set.add(x);
                }
            }

            System.out.println("YES");
        }
    }

    public static void main(String[] args) {
        new Solver().solve();
    }

    static class MyReader {
        BufferedReader br;
        StringTokenizer st;

        MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String res = "";
            try {
                res = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return res;
        }

        Integer[] nextIntArray(int n) {
            Integer[] arr = new Integer[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }

            return arr;
        }

        Long[] nextLongArray(int n) {
            Long[] arr = new Long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }

            return arr;
        }

        String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        }
    }

    static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }

}


