#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  string s;
  cin >> s;
  int cnt = 0;
  for (char c : s)
    if (c == 'a') cnt++;
  rep(_, cnt + 1) cout << 'a';
  cout << endl;
  return 0;
}