#include <cmath>
#include <iostream>
#include <stack>
#include <vector>

using std::cin;
using std::cout;
using std::max;
using std::min;
using std::stack;
using std::string;
using std::vector;

int main() {
  /*std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  std::cout.tie(0);*/
  stack<int> orig;
  stack<int> mini;
  int cmd;
  cin >> cmd;
  string req;
  int cnt = 0;
  for (int go = 0; go < cmd; ++go) {
    cin >> req;
    if (req == "enqueue") {
      cnt++;
      int num;
      cin >> num;
      int tomin = num;
      if (!mini.empty()) {
        tomin = min(mini.top(), num);
      }
      orig.push(num);
      mini.push(tomin);
      cout << "ok\n";
    } else if (req == "front") {
      if (cnt == 0) {
        cout << "error\n";
        continue;
      }
      cout << orig.top() << "\n";
    } else if (req == "clear") {
      while (cnt > 0) {
        cnt--;
        orig.pop();
        mini.pop();
      }
      cout << "ok\n";
    } else if (req == "size") {
      cout << cnt << "\n";
    } else if (req == "min") {
      if (cnt == 0) {
        cout << "error\n";
        continue;
      }
      cout << mini.top() << "\n";
    } else if (req == "dequeue") {
      if (cnt == 0) {
        cout << "error\n";
        continue;
      }
      cnt--;
      cout << orig.top() << "\n";
      orig.pop();
      mini.pop();
    }
  }
}