#include "testlib.h"
using namespace std;

int main() {
    registerValidation();

    const int MAX_Q = 800000;

    int Q = inf.readInt(1, MAX_Q, "Q");
    inf.readEoln();

    int len = 0;

    for (int i = 0; i < Q; i++) {
        int type = inf.readInt(1, 2, "query type");

        if (type == 1) {
            inf.readChar(' ');
            inf.readToken("[(|)]", "c");
            inf.readEoln();
            len++;
        } else {
            if (len == 0) {
                quitf(_pe, "query %d: delete from empty string", i + 1);
            }
            inf.readEoln();
            len--;
        }
    }

    inf.readEof();
    return 0;
}