#include <iostream>
#include <string>
bool firstUniqueChar(std::string &, char &);
int main()
{
    //line read from input
    std::string line;
    //word in read line
    std::string word;
    //the result of processing words, which contains all first unique characters in words
    std::string half_result;
    int pos;
    //the input can consist of one or more lines, so we'll process them all
    for(;std::getline(std::cin, line);)
    {
        //find the position of next ' '
        //if no matches were found, find returns string::npos
        while((pos = line.find(" ")) != std::string::npos)
        {
            //current word
            word = line.substr(0, pos);
            //cut this word including first ' ' from input string
            line.erase(0, pos + 1);
            //the input word can be empty. in this case we'll not process it
            if(!word.empty())
            {
                char c;
                if(firstUniqueChar(word, c))
                    half_result.append(1, c);
            }
        }
        //the rest of the line contains last word
        //it also can be empty
        if(!line.empty())
        {
            char c;
            if(firstUniqueChar(word, c))
                half_result.append(1, c);
        }
    }
    char c;
    if(!half_result.empty() && firstUniqueChar(half_result, c))
           std::cout<<std::endl<<c<<std::endl;
    else
            std::cout<<"<nothing>"<<std::endl;
    return 0;
}

bool firstUniqueChar(std::string &word, char &c)
{
    for(std::string::iterator it = word.begin(); it != word.end(); ++it)
    {
        //find occurence of current char in string Before current position
        int posB = (std::distance(word.begin(), it)) != 0 ? word.rfind(*it, std::distance(word.begin(), it) - 1) : std::string::npos;
        //find occurence of current char in string After current position
        int posA = (std::distance(word.begin(), it)) != word.size() - 1 ? word.find(*it, std::distance(word.begin(), it) + 1) : std::string::npos;
        if(posA == std::string::npos && posB == std::string::npos){
            c = *it;
            return true;
        }
    }
    return false;
}