#include<iostream>
#include<string>
#include<vector>
using namespace std;
int main () {
string s;
while (getline(cin, s)) {
int len = s.size();
string ans;
// 创建string类型的向量数组,并逐个把s中的字符按26个字母打进去
vector<string> arr(26);
for (int i = 0; i < len; ++i) {
arr[s[i] - 'a'].push_back(s[i]);
}
// 找到字符出现数量不为零的最小值
int minN = 100;
for (int i = 0; i < 26; ++i) {
if (arr[i].size() != 0 && arr[i].size() < minN)
minN = arr[i].size();
}
// 把符合要求的字符扔给新字符串并返回
for (int i = 0; i < len; ++i) {
if (arr[s[i] - 'a'].size() != 0 && arr[s[i] - 'a'].si***N)
ans += s[i];
}
cout << ans << endl;
}
return 0;
}