#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;
}