#include <iostream>
#include <vector>
#include <map>
#include <deque>
using namespace std;
#define ll long long

ostream& operator<<(ostream& os, vector<int>& input)
{
    for (auto i : input)
    {
        os << i << " ";
    }
    return os;
}

int main()
{
    cin.tie(nullptr);
    cout.tie(nullptr);
    ios_base::sync_with_stdio(false);
    int n;
    deque<int>q;
    cin >> n;
    while (n--)
    {
        int a;
        cin >> a;
        if (a == 0) q.push_back(0);
        else if (a == 1) q.push_back(1);
        else if (a == 2) q.pop_back();
        else if (a == 3)
        {
            int i = q.size() - 1;
            while (q[i] == 0)
            {
                q[i] = 1;
                i--;
            }
            q[i] = 0;
        }
        else if (a == 4)
        {
            int i = q.size() - 1;
            while (q[i] == 1)
            {
                q[i] = 0;
                i--;
            }
            q[i] = 1;
        }
    }
    cout << q.size() << endl;
    while (q.size() > 1 && q[0] == 0) q.pop_front();
    while (!q.empty())
    {
        cout << q.front();
        q.pop_front();
    }
    return 0;
}
/*
6
0 1 4 2 1 0
-3
-110

6
0 0 0 0 0 0
-6
-0
*/