#include <bits/stdc++.h>

using namespace std;
#define rep(i, n, o) for(int i = 0;i < (n);i++)
#define ou(x) cout << x << endl
#define ll long long
#define re return 0

int main(){
    string s;
    cin >> s;
    int cnt = 0;
    string a;
    for(auto ss: s){
        if(ss == 'a') cnt++;
    }
    rep(i, cnt + 1, 0){
        a += "a";
    }
    ou(a);
    re;
}