import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args)throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[] str = new String[N];
		for(int i =0;i<N;i++) {
			str[i]=sc.next();
		}

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	}
} import java.util.ArrayList; ArrayList java.util import java.util.Arrays; Arrays java.util import java.util.HashSet; HashSet java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args)throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[] str = new String[N];
		for(int i =0;i<N;i++) {
			str[i]=sc.next();
		}

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	}
} Main public static void main(String[] args)throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[] str = new String[N];
		for(int i =0;i<N;i++) {
			str[i]=sc.next();
		}

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[] str = new String[N];
		for(int i =0;i<N;i++) {
			str[i]=sc.next();
		}

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc String[] str = new String[N]; str new String[N] N for(int i =0;i<N;i++) {
			str[i]=sc.next();
		} int i =0; int i =0; i 0 i<N i N i++ i++ i {
			str[i]=sc.next();
		} {
			str[i]=sc.next();
		} str[i]=sc.next() str[i] str i sc.next() sc.next sc List<String> listA = new ArrayList<String>(Arrays.asList(str)); listA new ArrayList<String>(Arrays.asList(str)) List<String> listB = new ArrayList<String>(new HashSet<>(listA)); listB new ArrayList<String>(new HashSet<>(listA)) if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    } listA.size()==listB.size() listA.size() listA.size listA listB.size() listB.size listB {
	    	System.out.println("YES");
	    } System.out.println("YES") System.out.println System.out System System.out "YES" {
	    	System.out.println("NO");
	    } System.out.println("NO") System.out.println System.out System System.out "NO" String[] args args public class Main {
	public static void main(String[] args)throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[] str = new String[N];
		for(int i =0;i<N;i++) {
			str[i]=sc.next();
		}

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	}
} public class Main {
	public static void main(String[] args)throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[] str = new String[N];
		for(int i =0;i<N;i++) {
			str[i]=sc.next();
		}

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	}
} Main
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args)throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String[] str = new String[N];
		for(int i =0;i<N;i++) {
			str[i]=sc.next();
		}

	     List<String> listA = new ArrayList<String>(Arrays.asList(str));
	     List<String> listB = new ArrayList<String>(new HashSet<>(listA));

	    if(listA.size()==listB.size()) {
	    	System.out.println("YES");
	    }else {
	    	System.out.println("NO");
	    }
	}
}