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

typedef struct Node {
    int value;
    struct Node *left;
    struct Node *right;
} Node;


void insert(Node *node, int value) {
    if (node->value < value) {
        if (!node->left) {
            node->left = malloc(sizeof(*node));
            node->left->value = value;
        } else {
            insert(node->left, value);
        }
    } else if (node->value > value) {
        if (!node->right) {
            node->right = malloc(sizeof(*node));
            node->right->value = value;
        } else {
            insert(node->right, value);
        }
    }
}

void free_all(Node *node) {
    if (node) {
        free_all(node->left);
        printf("%d ", node->value);
        free_all(node->right);
        free(node);
    }
}

int main() {
    Node *head = NULL;
    _Bool first = true;
    _Bool empty = true;
    int sym;
    int last_sym = -1;
    while (scanf("%d", &sym) != EOF) {
        empty = false;
        if (sym == 0) {
            if (first) {
                first = false;
            } else {
                printf(" ");
            }
            free_all(head);
            printf("%d", 0);
            head = NULL;
        } else {
            if (!head) {
                head = calloc(1, sizeof(*head));
                head->value = sym;
            } else {
                insert(head, sym);
            }
        }
        last_sym = sym;
    }
    if (head) {
        if (last_sym != 0) {
            printf(" ");
        }
        free_all(head);
        printf("%d", 0);

    }
    if (!empty) {
        printf("\n");
    }
}