//code of JUYU ^ ^ never doubt youself !
#include <bits/stdc++.h>

#define For(i,a,b) for(int i=a;i<=b;i++) 
#define Rep(i,b,a) for(int i=a;i>=b;--i)
#define ms(a,b) memset(a,b,sizeof a)
#define fir first
#define sec second
#define eb emplace_back
#define pb push_back
#define mk make_pair

using namespace std;

typedef long long ll;
typedef pair<int,int> PII;

const int MOD = 1e9 + 7;
const int N = 1e5 + 10;

int ans;  //exactly you can get the answer

int main()
{
  string s; cin >> s; 
  int len = s.size();
  
  For(i,0,len-1) if (s[i] == 'a') ans ++;
  cout << 'a';
  For(i,1,ans) cout << 'a';
  cout << endl;
  
  return 0;
}
/* stuff you should look for
 * int overflow, array bounds
 * special cases (n=1?)
 * do smth instead of nothing and stay organized
 * WRITE STUFF DOWN
 * DON'T GET STUCK ON ONE APPROACH
 -- Benq
*/