import java.util.Scanner; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(System.in); char[] s = sc.next().toCharArray(); sc.close(); int cnt = 1; for (int i = 0; i < s.length; i++) { if (s[i] == 'a') { cnt++; } } StringBuilder sb = new StringBuilder(); for (int i = 0; i < cnt; i++) { sb.append('a'); } System.out.println(sb.toString()); } }