6的

#include <iostream>
#include <string>
using namespace std;

int main() {
    string s;
    getline(cin, s);
    string output = "";
    for (char c : s) {
        if (c == 'A' || c == 'C') {
            output.push_back(c);
        } else if (c == 'B') {
            if (!output.empty()) {
                output.pop_back();
            }
        }
    }
    cout << output << endl;
    return 0;
}