#include <iostream>
#include <vector>
#include <iterator>
#include <sstream>
#include <cmath>
#include <list>

std::string getLower(std::string str) {
    std::string newString = "";
    for (int i = 0; i < str.length(); ++i) {
        char current = std::tolower(str.at(i));
        newString += current;
    }
    return newString;
};

int main() {
    std::string input;
    std::getline(std::cin, input);
    std::stringstream stringstream(input);
    std::string str = "";
    std::vector<std::string> vector;
    while (stringstream >> str) {
        vector.push_back(str);
    }
    std::vector<std::string> result;
    for (int i = 0; i < vector.size(); ++i) {
        std::string current = getLower(vector[i]);
        vector.erase(vector.begin() + i);
        i--;
        int countRepeated = 1;
        for (int j = i + 1; j < vector.size(); ++j) {
            std::string currentString = getLower(vector[j]);
            if (current == currentString) {
                vector.erase(vector.begin() + j);
                j--;
                countRepeated++;
            }
        }
        if (countRepeated % 2 != 0) {
            result.push_back(current);
        }
    }
    for (int k = 0; k < result.size(); ++k) {
        if (k == result.size() - 1) {
            std::cout << result[k];
        } else {
            std::cout << result[k] << ", ";
        }
    }
    return 0;
}