#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, srt, end) for (long long i = (srt); i < (long long)(end); i++)

void solve() {
    string s;
    cin >> s;
    ll cnt = 0;
    for(auto e : s) cnt += e == 'a';
    cout << string(cnt+1, 'a') << endl;    
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}