include

include

include

include

include

include

using namespace std;

class S { private: string my_string{};

public: 

void append (string str){
    my_string.append(str);
}

void deletechar (int k){
    my_string.erase(my_string.size() - k);
}

void print(int k){
    cout << my_string[k-1] <<endl;
}

//constructor
S (string str)
:my_string{str} {}

S(){}

S &operator= ( const S &lhs){
    this->my_string = lhs.my_string;
    return *this;
}

};

int main() { /* Enter your code here. Read input from STDIN. Print output to STDOUT */ int Q; cin >> Q;

    int op;
    S my_string;

    stack<S> stk;

   while(Q--){
     cin >> op;
     string str;
     int k;
     switch(op) {
         case 1: 
         cin >> str;
         my_string.append(str);
         stk.push(my_string);
         break;

         case 2:
         cin >> k;
         my_string.deletechar(k);
         stk.push(my_string);
         break;

         case 3:
         cin >> k;
         my_string.print(k);
         break;

         case 4:
         if (!stk.empty()) {
                stk.pop();
                if (!stk.empty()) {
                    my_string = stk.top();
                } else {
                    my_string = S(); // Reset to default state if the stack is empty
                }
            }
            break;
         break;

         default:
         return 0;
     }  

   }
return 0;

}