#include <bits/stdc++.h>
#define MOD 998244353
#define mod 1000000007
#define ll long long
#define ull unsigned long long
#define ui unsigned int
using namespace std;
const int maxn = 1e6+9;
int main()
{
	int n;
	cin >> n;
	queue<int>q;
	for (int i = 1; i <= n; i++)
	{
	    char s;
        int x;
	    cin >> s;
	    if (s == '1')
	    {
	        cin >> x;
	        q.push(x); 
        }
        else if (s == '2')
        {
            if (q.empty()) cout << "ERR_CANNOT_POP\n";
            else q.pop();
        }
        else if (s == '3')
        {
            if (q.empty()) cout << "ERR_CANNOT_QUERY\n";
            else cout << q.front() << "\n";
        }
        else if (s == '4') cout << q.size();
    }
	return 0;
}