#include <set>
#include <map>
#include <string>
#include <iostream>

int main() {
    unsigned int T;
    std::cin >> T;
    std::map<char, std::set<char>> data;
    while(T--) {
        std::string line = "abc";
        std::cin >> line;
        data[line[0]];
        for(unsigned int i = 1; i < line.size(); i++) {
            data[line[i]].insert(line[i - 1]);
        }
    }
    std::string result;
    while(!data.empty()) {
        auto emptySet = data.begin();
        while(emptySet != data.end() && !emptySet -> second.empty()) {
            emptySet++;
        }
        if(emptySet == data.end()) {
            result = "SMTH WRONG";
            break;
        }
        auto current = emptySet -> first;
        result += current;
        data.erase(current);
        for(auto& p : data) {
            p.second.erase(current);
        }
    }
    std::cout << result << std::endl;
    return 0;
}