num=input()
dict1={}
# 1.统计字符个数,存放到dict中
for i in num:
    if i not in dict1:
        dict1[i]=1
    else:
        dict1[i]=dict1[i]+1

# 2.提取字典value,存放到list1中
list1=[]
for i in dict1.values():
    list1.append(i)

# 3.取出list1中的最小值
minnun=min(list1)

# 4.从dict1中取出最小值对应的key,放到list2中
list2=[]
for i in dict1:
    if dict1[i]==minnun:
        list2.append(i)

# 5.遍历字符串,如果字母不是最小值(也就说不是在list2中),则输出
str1=''
for i in num:
    if i not in list2:
        str1=str1+i
print(str1)