ABC_43 - B - バイナリハックイージー / Unhappy Hacking

#include <bits/stdc++.h>

#define forn(l, r) for(int i = l; i < (r); ++i)
#define forj(l, r) for(int j = l; j < (r); ++j)
#define TAM 1000100
#define SYNC ios::sync_with_stdio(0);
#define $ << ' ' <<
#define F first
#define S second
#define endl '\n'


using namespace std;

using ll = long long int;
using ii = pair<int, int>;
using vii = vector<ii>;
using vi = vector<int>;
using graph = vector<vi>;
const int INF = 0x3f3f3f3f;
const int MAXN = 112345;
const ll mod = 1000000007;

void printVec(vector<char> s) {
    for (int i = 0; i < (int) s.size(); ++i) {
        cout << s[i];
    }
}


int main() {
    //SYNC
    string s;
    vector<char> ans;
    cin >> s;
    for (int i = 0; i < (int) s.size(); ++i) {
        if(s[i] == 'B') {
            if (ans.size()){
                ans.pop_back();
            }
        } else {
            ans.push_back(s[i]);
        }
    }
    printVec(ans);
    cout << endl;
    return 0;
}