#include <bits/stdc++.h>
using namespace std;
int n;
string s;
const int MAXN = 5005;
struct Trie
{
    int tot = 0;
    int e[MAXN][2];
    bool ok[MAXN];
    void insert(const string &s)
    {
        int u = 0;
        for (int i = 0; i < s.length(); i++)
        {
            if (e[u][s[i] - '0'] == 0)
                e[u][s[i] - '0'] = ++tot;
            u = e[u][s[i] - '0'];
        }
        ok[u] = true;
    }
} trie;
int ans = -1;
const int MAXF = 0x3f3f3f3f;
int f[MAXN][MAXN];
queue<pair<int, int>> q;
void bfs()
{
    memset(f, 0x3f, sizeof(f));
    q.push(make_pair(0, 0));
    f[0][0] = 0;
    while (!q.empty())
    {
        int x = q.front().first, y = q.front().second;
        q.pop();
        if (trie.ok[x] && trie.ok[y] && x != y)
        {
            if (ans == -1)
                ans = f[x][y];
            else
                ans = min(ans, f[x][y]);
        }
        if (trie.e[x][0] && trie.e[y][0])
        {
            int nx = trie.e[x][0], ny = trie.e[y][0];
            if (f[nx][ny] == MAXF)
            {
                f[nx][ny] = f[x][y] + 1;
                q.push(make_pair(nx, ny));
            }
            if (trie.ok[nx] && f[0][ny] == MAXF)
            {
                f[0][ny] = f[x][y] + 1;
                q.push(make_pair(0, ny));
            }
            if (trie.ok[ny] && f[nx][0] == MAXF)
            {
                f[nx][0] = f[x][y] + 1;
                q.push(make_pair(nx, 0));
            }
        }
        if (trie.e[x][1] && trie.e[y][1])
        {
            int nx = trie.e[x][1], ny = trie.e[y][1];
            if (f[nx][ny] == MAXF)
            {
                f[nx][ny] = f[x][y] + 1;
                q.push(make_pair(nx, ny));
            }
            if (trie.ok[nx] && f[0][ny] == MAXF)
            {
                f[0][ny] = f[x][y] + 1;
                q.push(make_pair(0, ny));
            }
            if (trie.ok[ny] && f[nx][0] == MAXF)
            {
                f[nx][0] = f[x][y] + 1;
                q.push(make_pair(nx, 0));
            }
        }
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> s;
        trie.insert(s);
    }
    bfs();
    cout << ans << endl;
    return 0;
}