#include <iostream>
#include <fstream>
#include <vector>
#include <list>
#include <bits/stdc++.h>

#define SIZE 13109;

using namespace std;

int hashf(int n) {
    int i = 0;
    for(; n > 0; n /= 10)
        i = i * 10 + (n % 10);
    return i % SIZE;
}

int main() {
    vector <list <int>> hasht;
    vector <int> kkk;
    hasht.resize(13109);
    ifstream inp("input.txt");
    ofstream outp("output.txt");

    list<int>::iterator iter;
    int a;
    while (true) {
        inp >> a;
        if (a == 0) break;
        else if (a > 0) {
            bool exist = false;
            for (auto v : hasht[hashf(a)]) {
               if (v == a) {
                   exist = true;
                   break;
               }
            }
            if (!exist) {
                hasht[hashf(a)].push_back(a);
            }
        }
        else {
            for (iter = hasht[hashf(-a)].begin(); iter != hasht[hashf(-a)].end(); ++iter) {
                if (*iter == -a) {
                    hasht[hashf(-a)].remove(*iter);
                    break;
                }
            }
        }
    }

    for (int i = 0; i < hasht.size(); ++i){
        if (hasht[i].empty()) continue;
        for (auto v : hasht[i])
            kkk.push_back(v);
    }

    sort(kkk.begin(), kkk.end());

    for (auto j = kkk.begin(); j != kkk.end(); ++j)
        outp << *j << ' ';

    inp.close();
    outp.close();

    return 0;
}