#include <bits/stdc++.h>
using namespace std;

int n;
string s;
unordered_map<string, int> d, st;

int bfs()
{
    queue<string> q;
    q.push(s);
    d[s] = 0;
    st[s] = 1;

    while(q.size())
    {
        string t = q.front();
        q.pop();

        if(t.find("2012") != t.npos) return d[t];

        for(int i = 1; i < t.size(); i ++)
        {
            string tt = t;

            swap(tt[i - 1], tt[i]);

            if(!st[tt])
            {
                st[tt] = 1;
                q.push(tt);
                d[tt] = d[t] + 1;
            }
        }
    }

    return -1;
}

int main()
{
    cin >> n >> s;

    cout << bfs() << endl;

    return 0;
}