#include <iostream>
#include <algorithm>
#include <queue>
#include <cstdio>
#include <cctype>
#include <map>
#include <string>
#include <cstring>
#include <stack>
#include <set>
using namespace std;

class Command {
public:
    string op;
    int val;
}cmd_ins;

class Node {
public:
    Node *left;
    Node *right;
    int val;
} *root, *nodelist[40];

vector<Command> cmdList;
vector<int> postTravelArr;
stack<int> st;

void postTravel(Node *root) {
    if (root->left != NULL)
        postTravel(root->left);
    if (root->right != NULL)
        postTravel(root->right);
    postTravelArr.push_back(root->val);
}


int main() {
    int n;
    cin >> n;
    for (int i = 0; i < 2*n; i++) {
        cin >> cmd_ins.op;
        if (cmd_ins.op == "Push") {
            cin >> cmd_ins.val;
            st.push(cmd_ins.val);
        } else {
            cmd_ins.val = st.top();
            st.pop();
        }
        cmdList.push_back(cmd_ins);
        nodelist[cmd_ins.val] = new Node;
        nodelist[cmd_ins.val]->left = NULL;
        nodelist[cmd_ins.val]->right = NULL;
        nodelist[cmd_ins.val]->val = cmd_ins.val;
    }

    root = nodelist[cmdList[0].val];

    for (int i = 1; i < cmdList.size(); i++) {
        // attach much attention to Push operation
        // when two successive Push operation i-1 and i means Node i-1's left child is Node i
        // when one operation is Pop, and another operation is Push, so operation i-1 Pop and i Push means, Node i-1's right child is Node i 
        if (cmdList[i].op == "Push") {
            if (cmdList[i-1].op == "Push") nodelist[cmdList[i-1].val]->left = nodelist[cmdList[i].val];
            else nodelist[cmdList[i-1].val]->right = nodelist[cmdList[i].val];
        }
    }

    postTravel(root);
    cout << postTravelArr[0];
    for (int i = 1; i< postTravelArr.size(); i++) {
        cout << " " << postTravelArr[i];
    }
    cout << endl;
    return 0;
}