def main():
    s = list(input())
    a_num = 0
    for ch in s:
        if ch == "a":
            a_num += 1

    ans = ""
    if a_num > 0:
        ans += "a" * (a_num + 1)
    else:
        ans = "a"
    print(ans)


if __name__ == "__main__":
    main()