#include <bits/stdc++.h>
using namespace std;
int main() 
{
    string line;
    getline(cin, line);
    size_t pos = line.find(' ');
    string s1 = line.substr(0, pos);
    string s2 = line.substr(pos + 1, line.size());
    s1.append(s2);
    vector<char> vodd;
    vector<char> veven;
    for(int i = 0; i < s1.size(); ++i) {
        if(i % 2 == 0) veven.push_back(s1[i]);
        else vodd.push_back(s1[i]);
    }
    sort(vodd.begin(), vodd.end());
    sort(veven.begin(), veven.end());
    string ss = "";
    int i = 0;
    for(; i < vodd.size() && i < veven.size(); ++i) {
        ss.push_back(veven[i]);
        ss.push_back(vodd[i]);
    }
    while(i < vodd.size()) ss.push_back(vodd[i++]);
    while(i < veven.size()) ss.push_back(veven[i++]);
    //0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111
    //1000 0100 1100 0010 1010 0110 1110 0001 1001 0101 1101 0011 1011 0111 1111
    // 直接打出映射即可
    string code = "123456789abcdefABCDEF";
    string key  = "84C2A6E195D3B7F5D3B7F";
    string res = "";
    for(int i = 0; i < ss.size(); ++i) {
        if(code.find(ss[i]) != string::npos) {
            res.push_back(key[code.find(ss[i])]);
        } else res.push_back(ss[i]);
    }
    cout << res;
}