import java.util.*;
import java.io.PrintWriter;
import static java.lang.Integer.*;
import static java.lang.Long.*;
import static java.lang.Math.*;
import static java.lang.System.*;

public class Main {
	public static final int MOD = 1000000007;
	public static ArrayList<Integer> list = new ArrayList<>();
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int n = parseInt(sc.next());
		long[] a = new long[n];
		for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		}
		sc.close();
		HashSet<Long> set = new HashSet<>(n);
		boolean f=true;
		for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		}
		out.println(f?"YES":"NO");
	}
} import java.util.*; util.* java import java.io.PrintWriter; PrintWriter java.io import static java.lang.Integer.*; import static java.lang.Integer.*; import static java.lang.Integer.*; import static java.lang.Long.*; import static java.lang.Long.*; import static java.lang.Long.*; import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.System.*; import static java.lang.System.*; import static java.lang.System.*; public class Main {
	public static final int MOD = 1000000007;
	public static ArrayList<Integer> list = new ArrayList<>();
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int n = parseInt(sc.next());
		long[] a = new long[n];
		for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		}
		sc.close();
		HashSet<Long> set = new HashSet<>(n);
		boolean f=true;
		for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		}
		out.println(f?"YES":"NO");
	}
} Main public static final int MOD = 1000000007; MOD 1000000007 public static ArrayList<Integer> list = new ArrayList<>(); list new ArrayList<>() public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int n = parseInt(sc.next());
		long[] a = new long[n];
		for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		}
		sc.close();
		HashSet<Long> set = new HashSet<>(n);
		boolean f=true;
		for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		}
		out.println(f?"YES":"NO");
	} main {
		int i,j;
		Scanner sc = new Scanner(in);
		int n = parseInt(sc.next());
		long[] a = new long[n];
		for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		}
		sc.close();
		HashSet<Long> set = new HashSet<>(n);
		boolean f=true;
		for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		}
		out.println(f?"YES":"NO");
	} int i i j; j Scanner sc = new Scanner(in); sc new Scanner(in) int n = parseInt(sc.next()); n parseInt(sc.next()) parseInt sc.next() sc.next sc long[] a = new long[n]; a new long[n] n for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		} i = 0; i = 0 i 0 i < a.length i a.length a a.length i++ i++ i {
			a[i] = parseLong(sc.next());
		} {
			a[i] = parseLong(sc.next());
		} a[i] = parseLong(sc.next()) a[i] a i parseLong(sc.next()) parseLong sc.next() sc.next sc sc.close() sc.close sc HashSet<Long> set = new HashSet<>(n); set new HashSet<>(n) boolean f=true; f true for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		} i = 0; i = 0 i 0 i < n i n i++ i++ i {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		} {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		} if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			} set.contains(a[i]) set.contains set a[i] a i {
				f=false;
				break;
			} f=false f false break; {
				set.add(a[i]);
			} set.add(a[i]) set.add set a[i] a i out.println(f?"YES":"NO") out.println out f?"YES":"NO" f "YES" "NO" String[] args args public class Main {
	public static final int MOD = 1000000007;
	public static ArrayList<Integer> list = new ArrayList<>();
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int n = parseInt(sc.next());
		long[] a = new long[n];
		for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		}
		sc.close();
		HashSet<Long> set = new HashSet<>(n);
		boolean f=true;
		for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		}
		out.println(f?"YES":"NO");
	}
} public class Main {
	public static final int MOD = 1000000007;
	public static ArrayList<Integer> list = new ArrayList<>();
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int n = parseInt(sc.next());
		long[] a = new long[n];
		for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		}
		sc.close();
		HashSet<Long> set = new HashSet<>(n);
		boolean f=true;
		for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		}
		out.println(f?"YES":"NO");
	}
} Main
import java.util.*;
import java.io.PrintWriter;
import static java.lang.Integer.*;
import static java.lang.Long.*;
import static java.lang.Math.*;
import static java.lang.System.*;

public class Main {
	public static final int MOD = 1000000007;
	public static ArrayList<Integer> list = new ArrayList<>();
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int n = parseInt(sc.next());
		long[] a = new long[n];
		for (i = 0; i < a.length; i++) {
			a[i] = parseLong(sc.next());
		}
		sc.close();
		HashSet<Long> set = new HashSet<>(n);
		boolean f=true;
		for (i = 0; i < n; i++) {
			if(set.contains(a[i])) {
				f=false;
				break;
			} else {
				set.add(a[i]);
			}
		}
		out.println(f?"YES":"NO");
	}
}
