// 不知道满不满足要求 #include <iostream> #include <vector> #include <string> #include <cstring> using namespace std; int main() { string str; while (cin >> str) { vector<char> vec; for (char ch : str) { int index = -1; for (int i = 0; i < vec.size(); ++i) { if (vec[i] == ch) { index = i; break; } } if (index == -1) { vec.push_back(ch); } else if (index != vec.size() - 1 && vec[index] < vec[index + 1]) { continue; } else { while (index < vec.size() - 1) { vec[index] = vec[index + 1]; ++index; } vec[index] = ch; } } for (char ch : vec) { cout << ch; } cout << endl; } return 0; }