func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s, t;     cin >> s;     for (int i = s.length() - 1; i >= 0; i--) {       if (t ==   ) {         t.push_back(s[i]);       } else if (t.back() <= s[i]) {         t.push_back(s[i]);       }     }     reverse(t.begin(), t.end());     cout << t;   }   