import java.util.*;
public class Main
{
  public static void main(String[] args)
  {
    Scanner s=new Scanner(System.in);
    int n=s.nextInt();
   int a[]=new int[n];
   HashSet<Integer> h=new HashSet<Integer>();
boolean b=true;
  for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
}
if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   }
}
}

   
 import java.util.*; util.* java public class Main
{
  public static void main(String[] args)
  {
    Scanner s=new Scanner(System.in);
    int n=s.nextInt();
   int a[]=new int[n];
   HashSet<Integer> h=new HashSet<Integer>();
boolean b=true;
  for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
}
if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   }
}
} Main public static void main(String[] args)
  {
    Scanner s=new Scanner(System.in);
    int n=s.nextInt();
   int a[]=new int[n];
   HashSet<Integer> h=new HashSet<Integer>();
boolean b=true;
  for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
}
if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   }
} main {
    Scanner s=new Scanner(System.in);
    int n=s.nextInt();
   int a[]=new int[n];
   HashSet<Integer> h=new HashSet<Integer>();
boolean b=true;
  for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
}
if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   }
} Scanner s=new Scanner(System.in); s new Scanner(System.in) int n=s.nextInt(); n s.nextInt() s.nextInt s int a[]=new int[n]; a new int[n] n HashSet<Integer> h=new HashSet<Integer>(); h new HashSet<Integer>() boolean b=true; b true for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
} int i=0; int i=0; i 0 i<n i n i++ i++ i {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
} {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
} a[i]=s.nextInt() a[i] a i s.nextInt() s.nextInt s if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
} b {
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
} if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
} h.contains(a[i]) h.contains h a[i] a i b=false b false {
h.add(a[i]);
} h.add(a[i]) h.add h a[i] a i if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   } b 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)
  {
    Scanner s=new Scanner(System.in);
    int n=s.nextInt();
   int a[]=new int[n];
   HashSet<Integer> h=new HashSet<Integer>();
boolean b=true;
  for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
}
if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   }
}
} public class Main
{
  public static void main(String[] args)
  {
    Scanner s=new Scanner(System.in);
    int n=s.nextInt();
   int a[]=new int[n];
   HashSet<Integer> h=new HashSet<Integer>();
boolean b=true;
  for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
}
if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   }
}
} Main
import java.util.*;
public class Main
{
  public static void main(String[] args)
  {
    Scanner s=new Scanner(System.in);
    int n=s.nextInt();
   int a[]=new int[n];
   HashSet<Integer> h=new HashSet<Integer>();
boolean b=true;
  for(int i=0;i<n;i++)
  {
    a[i]=s.nextInt();
if(b)
{
if(h.contains(a[i]))
b=false;
else
{
h.add(a[i]);
}
}
}
if(b)
System.out.println("YES");
else
    {
     System.out.println("NO");
   }
}
}

   

