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

typedef struct Pair
{
    int value;
    int times;
} Pair;

typedef struct Node
{
    Pair pair;
    struct Node *prev;
    struct Node *next;
} Node;

void print_pair(Node *ptr) {
    if (ptr == NULL) {
        printf("%s", "NULL");
    } else {
        printf("%d %d", ptr->pair.value, ptr->pair.times);
    }

    // printf("");
}

void add_in_start(Node **head_ref, Node **tail_ref, Pair value) {
    Node *new_node = malloc(sizeof(Node));
    new_node->pair = value;

    new_node->next = *head_ref;
    new_node->prev = NULL;

    if (*head_ref != NULL) {
        (*head_ref)->prev = new_node;
    } else {  // head_ref == NULL <=> tail_ref == NULL
        *tail_ref = new_node;
    }

    *head_ref = new_node;
}

void remove_node(Node **head_ref, Node **tail_ref, Node *node_ref) {
    if (node_ref->prev != NULL) {
        node_ref->prev->next = node_ref->next;
    } else {
        *head_ref = node_ref->next;
    }

    if (node_ref->next != NULL) {
        node_ref->next->prev = node_ref->prev;
    } else {
        *tail_ref = node_ref->prev;
    }

    free(node_ref);
}

void add(Node **head_ref, Node **tail_ref, int number) {
    Node *ptr = *head_ref;

    while (ptr != NULL) {
        if (ptr->pair.value == number) {
            Pair new_pair = (Pair) { ptr->pair.value, ptr->pair.times + 1 };
            remove_node(head_ref, tail_ref, ptr);
            add_in_start(head_ref, tail_ref, new_pair);
            return;
        }

        ptr = ptr->next;
    }

    add_in_start(head_ref, tail_ref, (Pair) { number, 1 });
}

void print_from_head(Node **head_ref) {
    Node *ptr = *head_ref;

    while (ptr != NULL) {
        print_pair(ptr->prev);
        print_pair(ptr);
        print_pair(ptr->next);
        printf("%s", "\n");

        ptr = ptr->next;
    }
}

void print_from_tail(Node **tail_ref) {
    Node *ptr = *tail_ref;

    while (ptr != NULL) {
        // print_pair(ptr->prev);
        print_pair(ptr);
        // print_pair(ptr->next);
        printf("%s", "\n");

        ptr = ptr->prev;
    }
}

void free_list(Node **head_ref) {
    Node *ptr = *head_ref;

    while (ptr != NULL) {
        Node *tmp = ptr->next;
        free(ptr);
        ptr = tmp;
    }
}

int main() {
    Node *head = NULL;
    Node *tail = NULL;

    int number;
    while (scanf("%d", &number) == 1) {
        add(&head, &tail, number);
        // print_from_head(&head);
    }

    /*
    add_in_start(&head, &tail, (Pair) {1, 1});
    add_in_start(&head, &tail, (Pair) {2, 1});
    add_in_start(&head, &tail, (Pair) {3, 1});
    add_in_start(&head, &tail, (Pair) {4, 1});
    remove_node(&head, &tail, head->next);
    remove_node(&head, &tail, tail->prev);
    remove_node(&head, &tail, tail);
    remove_node(&head, &tail, head);
    */

    print_from_tail(&tail);

    free_list(&head);

    return 0;
}