include<iostream> #include<string> #include<unordered_set> #include<algorithm> using namespace std; int main() { int num = 0; string ans; cin >> num; unordered_set<char> nums; string str = to_string(num); reverse(str.begin(), str.end()); for (char c : str) { if(!nums.count(c)) //如果nums中不存在c { ans += c; nums.insert(c); } } cout<<stoi(ans); return 0; }