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

struct Node {
    char data[10];
    struct Node* prev;
    struct Node* next;
};

struct Node* createNode(char* data){
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    strcpy(newNode->data, data);
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}

void append(struct Node** head, char* data){
    struct Node* newNode = createNode(data);
    if(*head == NULL){
        *head = newNode;
        return;
    }
    struct Node* temp = *head;
    while(temp->next != NULL){
        temp = temp->next;
    }
    temp->next = newNode;
    newNode->prev = temp;
}

void deletepos(struct Node** head, int pos){
    struct Node* temp = *head;
    int index = 0;
    while(temp != NULL && index < pos){
        temp = temp->next;
        index++;
    }
    if(temp == NULL){
        printf("Invalid input");
        exit(0);
    }
    if(temp->prev == NULL){
        *head = temp->next;
        if(*head != NULL) (*head)->prev = NULL;
    } else {
        temp->prev->next = temp->next;
        if(temp->next != NULL){
            temp->next->prev = temp->prev;
        }
    }
    free(temp);
}

void printlist(struct Node* head){
    if(head == NULL){
        printf("List is empty\n");
        return;
    }
    struct Node* temp = head;
    while(temp != NULL){
        printf("%s ", temp->data);
        temp = temp->next;
    }
    printf("\n");
}

int isvalidname(char* str){
    if(!isalpha(str[0])) return 0;
    for(int i = 1; str[i] != '\0'; i++){
        if(!isalnum(str[i])) return 0;
    }
    return 1;
}

int main(){
    int n, pos;
    if(scanf("%d", &n) != 1 || n < 1 || n > 1000){
        printf("Invalid input\n");
        return 0;
    }
    struct Node* head = NULL;
    for(int i = 0; i < n; i++){
        char buffer[10];
        if(scanf("%s", buffer) != 1 || !isvalidname(buffer)){
            printf("Invalid input\n");
            return 0;
        }
        append(&head, buffer);
    }
    if(scanf("%d", &pos) !=