import java.util.*;
 
class Main {
  public static void main(String[] args) {
    
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int[] A = new int[N];
    for (int i = 0; i < N; i++) {
    A[i] = sc.nextInt();
    }
    
    Arrays.sort(A);
   
    boolean flg = true;
    for(int j = 0; j < N-1; j++) {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		}

    if (flg) {
      System.out.print("YES");
    } else {
      System.out.print("NO");
    }
  }
} import java.util.*; util.* java class Main {
  public static void main(String[] args) {
    
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int[] A = new int[N];
    for (int i = 0; i < N; i++) {
    A[i] = sc.nextInt();
    }
    
    Arrays.sort(A);
   
    boolean flg = true;
    for(int j = 0; j < N-1; j++) {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		}

    if (flg) {
      System.out.print("YES");
    } else {
      System.out.print("NO");
    }
  }
} Main public static void main(String[] args) {
    
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int[] A = new int[N];
    for (int i = 0; i < N; i++) {
    A[i] = sc.nextInt();
    }
    
    Arrays.sort(A);
   
    boolean flg = true;
    for(int j = 0; j < N-1; j++) {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		}

    if (flg) {
      System.out.print("YES");
    } else {
      System.out.print("NO");
    }
  } main {
    
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int[] A = new int[N];
    for (int i = 0; i < N; i++) {
    A[i] = sc.nextInt();
    }
    
    Arrays.sort(A);
   
    boolean flg = true;
    for(int j = 0; j < N-1; j++) {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		}

    if (flg) {
      System.out.print("YES");
    } else {
      System.out.print("NO");
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] A = new int[N]; A new int[N] N for (int i = 0; i < N; i++) {
    A[i] = sc.nextInt();
    } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
    A[i] = sc.nextInt();
    } {
    A[i] = sc.nextInt();
    } A[i] = sc.nextInt() A[i] A i sc.nextInt() sc.nextInt sc Arrays.sort(A) Arrays.sort Arrays A boolean flg = true; flg true for(int j = 0; j < N-1; j++) {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		} int j = 0; int j = 0; j 0 j < N-1 j N-1 N 1 j++ j++ j {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		} {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		} if (A[j] == A[j+1]) {
			  flg = false;
			} A[j] == A[j+1] A[j] A j A[j+1] A j+1 j 1 {
			  flg = false;
			} flg = false flg false if (flg) {
      System.out.print("YES");
    } else {
      System.out.print("NO");
    } flg {
      System.out.print("YES");
    } System.out.print("YES") System.out.print System.out System System.out "YES" {
      System.out.print("NO");
    } System.out.print("NO") System.out.print System.out System System.out "NO" String[] args args
import java.util.*;
 
class Main {
  public static void main(String[] args) {
    
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int[] A = new int[N];
    for (int i = 0; i < N; i++) {
    A[i] = sc.nextInt();
    }
    
    Arrays.sort(A);
   
    boolean flg = true;
    for(int j = 0; j < N-1; j++) {
      if (A[j] == A[j+1]) {
			  flg = false;
			}
		}

    if (flg) {
      System.out.print("YES");
    } else {
      System.out.print("NO");
    }
  }
}