#include <conio.h>
#include <fstream>
#include <iostream>
#include <map>
#include <vector>
using namespace std;

vector<size_t> usedPoints;
vector<pair<size_t, size_t>> pairs;

static bool isInside(map<size_t, vector<size_t>>& map, const size_t& key) {
  return map.find(key) != map.end();
}

static bool isUsed(const size_t& key) {
  for (auto& jt : usedPoints) {
    if (jt == key) {
      return true;
    }
  }
  return false;
}

static bool isFound(map<size_t, vector<size_t>>& map,
                    const size_t& lookingIn,
                    const size_t& lookingFor) {
  usedPoints.push_back(lookingIn);
  for (auto& it : map[lookingIn]) {
    if (it == lookingFor) {
      usedPoints.clear();
      return true;
    }
    if (!isUsed(it)) {
      return isFound(map, it, lookingFor);
    }
  }
  usedPoints.clear();
  return false;
}

int main() {
  size_t pairAmount, choice;
  map<size_t, vector<size_t>> pointMap;
  ifstream input("input.txt");
  if (!input.is_open()) {
    cout << "File not found.";
    return -1;
  }

  cout << "Select input type (1 - file; 2 - console): ";
  cin >> choice;
  if (choice != 1 && choice != 2) {
    cout << "Wrong type, please pick 1 or 2";
    return -1;
  }
  size_t first, second;
  if (choice == 1) {
    while (input.peek() != EOF) {
      input >> first >> second;
      if (isInside(pointMap, first) || isInside(pointMap, second)) {
        if (isFound(pointMap, first, second)) {
        } else {
          pointMap[first].push_back(second);
          pointMap[second].push_back(first);
          pairs.push_back(pair<size_t, size_t>(first, second));
        }
      } else {
        pointMap[first].push_back(second);
        pointMap[second].push_back(first);
        pairs.push_back(pair<size_t, size_t>(first, second));
      }
    }
  } else {
    cout << "Enter the amount of pairs you want to enter later: ";
    cin >> pairAmount;

    cout << endl << "Enter pairs: " << endl;
    for (size_t i = 0; i < pairAmount; i++) {
      cout << i + 1 << ") ";
      cin >> first >> second;
      if (isInside(pointMap, first) || isInside(pointMap, second)) {
        if (isFound(pointMap, first, second)) {
        } else {
          pointMap[first].push_back(second);
          pointMap[second].push_back(first);
          pairs.push_back(pair<size_t, size_t>(first, second));
        }
      } else {
        pointMap[first].push_back(second);
        pointMap[second].push_back(first);
        pairs.push_back(pair<size_t, size_t>(first, second));
      }
    }
  }
  cout << endl;
  for (auto& it : pairs) {
    cout << it.first << "-" << it.second << " ";
  }
  return 0;
}