import java.util.Scanner;
import java.util.Arrays;

public class Main{
public static void main(String[] args){
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
int[] a=new int[n];

int i=0;
for(i=0;i<n;i++){
    a[i]=scan.nextInt();
}

Arrays.sort(a);
int sum=0;
for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
}

if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
}

}
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays java.util public class Main{
public static void main(String[] args){
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
int[] a=new int[n];

int i=0;
for(i=0;i<n;i++){
    a[i]=scan.nextInt();
}

Arrays.sort(a);
int sum=0;
for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
}

if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
}

}
} Main public static void main(String[] args){
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
int[] a=new int[n];

int i=0;
for(i=0;i<n;i++){
    a[i]=scan.nextInt();
}

Arrays.sort(a);
int sum=0;
for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
}

if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
}

} main {
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
int[] a=new int[n];

int i=0;
for(i=0;i<n;i++){
    a[i]=scan.nextInt();
}

Arrays.sort(a);
int sum=0;
for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
}

if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
}

} Scanner scan=new Scanner(System.in); scan new Scanner(System.in) int n=scan.nextInt(); n scan.nextInt() scan.nextInt scan int[] a=new int[n]; a new int[n] n int i=0; i 0 for(i=0;i<n;i++){
    a[i]=scan.nextInt();
} i=0; i=0 i 0 i<n i n i++ i++ i {
    a[i]=scan.nextInt();
} {
    a[i]=scan.nextInt();
} a[i]=scan.nextInt() a[i] a i scan.nextInt() scan.nextInt scan Arrays.sort(a) Arrays.sort Arrays a int sum=0; sum 0 for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
} i=0; i=0 i 0 i<n-1 i n-1 n 1 i++ i++ i {
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
} {
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
} if(a[i]==a[i+1]){
        sum=sum+1;
    } a[i]==a[i+1] a[i] a i a[i+1] a i+1 i 1 {
        sum=sum+1;
    } sum=sum+1 sum sum+1 sum 1 if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
} sum==0 sum 0 {
    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){
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
int[] a=new int[n];

int i=0;
for(i=0;i<n;i++){
    a[i]=scan.nextInt();
}

Arrays.sort(a);
int sum=0;
for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
}

if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
}

}
} public class Main{
public static void main(String[] args){
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
int[] a=new int[n];

int i=0;
for(i=0;i<n;i++){
    a[i]=scan.nextInt();
}

Arrays.sort(a);
int sum=0;
for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
}

if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
}

}
} Main
import java.util.Scanner;
import java.util.Arrays;

public class Main{
public static void main(String[] args){
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
int[] a=new int[n];

int i=0;
for(i=0;i<n;i++){
    a[i]=scan.nextInt();
}

Arrays.sort(a);
int sum=0;
for(i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
        sum=sum+1;
    }
}

if(sum==0){
    System.out.println("YES");
}else{
    System.out.println("NO");
}

}
}