#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <algorithm>
#include <numeric>
#include <functional>
#include <set>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cctype>
#include <climits>
#include <fstream>
#include <time.h>

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define FORE(i,a,b) for(int i=(a);i<=(b);++i)
#define REP(i,n) FOR(i,0,n)
#define REPE(i,n) FORE(i,0,n)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0L)

using namespace std;

struct MiddleCode {
    string s;
    string encode(string _s) {
        s = _s;
        string t = "";
        while (s.size() != 0) {
            int half = s.size() / 2;
            int del_idx = half;
            if (s.size() % 2 == 0 && s[half - 1] < s[half]) {
                del_idx = half - 1;
            }
            t += s[del_idx];
            s.erase(del_idx, 1);
        }
        return t;
    }
};