#include <iostream>
#include <deque>

using namespace std;

int i,n,a,j,sor;
deque <int> v;

int main()
{
    cin>>n;
    v.push_back(0);

    for (i=1; i<=n; ++i)
    {
        cin>>a;

        if (a==0)
        {
            v.push_back(0);
            ++sor;
        }
        else if (a==1)
        {
            v.push_back(1);
            ++sor;
        }
        else if (a==2)
        {
            v.pop_back();
            --sor;
        }
        else if (a==3)
        {
            if (v.back()==1) v.back()=0;
            else
            {
                j=v.size()-1;
                while (v[j]==0)
                {
                    v[j]=1;
                    --j;
                }
                v[j]=0;
            }
        }
        else if (a==4)
        {
            if (v.back()==0) v.back()=1;
            else
            {
                j=v.size()-1;
                while (v[j]==1)
                {
                    v[j]=0;
                    --j;
                }
                v[j]=1;
            }
        }
    }

    while (v.size()>1 && v.front()==0) v.pop_front();

    cout<<sor<<"\n";

    for (auto &e:v)
    {
        cout<<e;
    }

    return 0;
}
//6 0 1 4 2 1 0

//6 0 0 0 0 0 0