#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <map>
#include <queue>
#include <cmath>
using namespace std;
typedef long long ll;
#define rep(i, n) for (int i=0;i < (int)(n);i++)

int main(){
    string s;
    cin >> s;
    string ans;
    for (int i = 0; i < int(s.size());i++){
        if (s[i] == 'a') ans.push_back('a');
    }
    cout << ans+"a" << endl;
    

    return 0;
}