/**
 *    author:  ytsmash
 *    created: 14.08.2021 08:58:52
 **/

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define all(x) x.begin(), x.end()
const long double EPS = 1e-10;
const long long INF = 1e18;
const long double PI = acos(-1.0L);
using P = pair<int, int>;

int main() {
    string S;
    cin >> S;
    int cnt = 0;
    rep(i, S.size()) {
        if (S[i] == 'a') {
            cnt++;
        }
    }
    rep(i, cnt+1) {
        cout << 'a';
    }
    cout << "\n";
}