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#include <iostream>
#include <fstream>

using namespace std;

struct Node {
    Node* l;
    Node* r;
    int val;
    Node(int val) :val(val), l(nullptr), r(nullptr) {}
};

Node* root = nullptr;

ifstream fin("input.txt");
ofstream fout("output.txt");

void add(int cur_val, Node* cur) {
    if (cur == nullptr) {
        root = new Node(cur_val);
        return;
    }
    if (cur_val < cur->val) {
        if (cur->l == nullptr) {
            cur->l = new Node(cur_val);
            return;
        }
        add(cur_val, cur->l);
    }
    else if (cur_val > cur->val) {
        if (cur->r == nullptr) {
            cur->r = new Node(cur_val);
            return;
        }
        add(cur_val, cur->r);
    }
}

void print(Node* cur) {
    if (cur == nullptr) return;
    print(cur->l);
    fout << cur->val << "\n";
    print(cur->r);
}

int main() {

    int a; fin >> a;
    while (a != 0) {
        add(a, root);
        fin >> a;
    }
    print(root);

    fin.close();
    fout.close();
    return 0;
}