class Solution {
public:
    string customSortString(string order, string s) {
        vector<int> freq(26);
        for (char ch: s) {
            ++freq[ch - 'a'];
        }
        string ans;
        for (char ch: order) {
            if (freq[ch - 'a'] > 0) {
                ans += string(freq[ch - 'a'], ch);
                freq[ch - 'a'] = 0;
            }
        }
        for (int i = 0; i < 26; ++i) {
            if (freq[i] > 0) {
                ans += string(freq[i], i + 'a');
            }
        }
        return ans;
    }
};