spf = [i for i in range(10**5)]
for i in range(2,10**5):
    if spf[i]!=i:
        continue
    for j in range(2*i,10**5,i):
        spf[j] = i

def factorization(n):
    res = []
    for i in range(2,n+1):
        if i**2 > n:
            break
        if n%i==0:
            assert spf[i]==i
            cnt = 0
            while n%i==0:
                cnt += 1
                n //= i
            res.append((i,cnt))
    if n!=1:
        res.append((n,1))
    return res

def divisors(n):
    res = []
    for i in range(2,n+1):
        if i**2 >= n:
            break
        if n%i==0:
            res.append(i)
            res.append(n//i)
    if i**2==n:
        res.append(i)
    return res

import sys,random,bisect
from collections import deque,defaultdict
from heapq import heapify,heappop,heappush
from itertools import permutations
from math import gcd,log

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

s = input()
t = s.count("a")
print("a" * (t+1))