# import sys
# #sys.setrecursionlimit(1000000)
# input = sys.stdin.readline
def mp():return map(int,input().split())
def lmp():return list(map(int,input().split()))
import math
import bisect
from copy import deepcopy as dc
from itertools import accumulate
from collections import Counter, defaultdict, deque
import itertools
def ceil(U,V):return (U+V-1)//V
def modf1(N,MOD):return (N-1)%MOD+1
inf = int(1e30)
mod = int(1e9+7)
def rle(lst):
    ans = []
    cnt = 1
    ini = lst[0]
    for i in range(1, len(lst)):
        if ini == lst[i]:cnt += 1
        else:
            ans.append((ini, cnt))
            cnt = 1
            ini = lst[i]
    ans.append((ini, cnt))
    return ans

s = list(input())
r = rle(s)
cnt = 0
for i,j in r:
    if i == "a":cnt = max(cnt,j)
print("a"*cnt+"a")