#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

int main() {
    string str;

    ifstream inp("input.txt");
    inp >> str;
    inp.close();

    int r = str.size() - 1;
    int l = 0;

    while (l != str.size()) {
        if (str[l] == str[r]) {
            r--;
        }
        l++;
    }

    ofstream out("output.txt");
    for (int i = r; i >= 0; --i) {
        out << str[i];
    }
    out.close();
    return 0;
}