#include<stdio.h>
#include<stdlib.h>

typedef struct Node{
    char data;
    struct Node *prev;
    struct Node *next;
}node;

node *head = NULL, *tail;

void create(char *ch){
    node *newNode = (node*) malloc (1 * sizeof(node));
    newNode->data = *ch;
    newNode->next = NULL;
    newNode->prev = NULL;
    if(head = NULL){
        head = newNode;
        tail = newNode;
    }
    else{
        newNode->prev = tail;
        tail->next = newNode;
        tail = newNode;
    }
}

void check(){
    node *itr, *iter;
    for(itr=head;itr!=NULL;itr=itr->next){
        for(iter=itr->next;iter!=NULL;iter=iter->next){
            if(itr->data == iter->data){
                iter->prev->next = iter->next;
                iter->next->prev = iter->prev;
            }
        }
    }
}

void display(){
    node *itr;
    for(itr=head;itr!=NULL;itr=itr->next){
        printf("%c",itr->data);
    }
}

int main(){
    int n,itr;
    char ch;
    scanf("%d",&n);
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    for(itr=0;itr<n;itr++){
        scanf("%c",ch);
        create(ch);
    }
    check();
    display();
}