#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
#define ull unsigned long long
#define ms(x, y) memset(x, y, sizeof x);
#define debug(x) cout << #x << " = " << x << endl;
#define ios ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#define fre                           \
    freopen("input.txt", "r", stdin); \
    freopen("output.txt", "w", stdout);
const int mod = 998244353;
const int inf = 0x3f3f3f3f3f3f3f3f;
const int N = 1e6 + 10;
const double esp = 1e-6;
const ull MOD1 = 1610612741;
const ull MOD2 = 805306457;
const ull BASE1 = 1331;
const ull BASE2 = 131;
#define pre(i, a, b) for (int i = a; i <= b; i++)
#define rep(i, a, b) for (int i = a; i >= b; i--)
#define all(x) (x).begin(), (x).end()
char *p1, *p2, buf[100000]; // 快读和同步流二者只能选一个
#define nc() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2) ? EOF : *p1++)
int read()
{
    int x = 0, f = 1;
    char ch = nc();
    while (ch < 48 || ch > 57)
    {
        if (ch == '-')
            f = -1;
        ch = nc();
    }
    while (ch >= 48 && ch <= 57)
        x = x * 10 + ch - 48, ch = nc();
    return x * f;
}
void write(int x)
{
    if (x < 0)
        putchar('-'), x = -x;
    if (x > 9)
        write(x / 10);
    putchar(x % 10 + '0');
    return;
}
int n;
string s[N];
void solve()
{
    cin >> n;
    map<int, vector<string>> mp;
    pre(i, 1, n)
    {
        cin >> s[i];
        int tp = s[i].size();
        mp[tp].push_back(s[i]);
    }
    // max 1000
    map<string, int> mm;
    int now = 1;
    for (auto [a, y] : mp)
    {
        if (a != now)
        {
            cout << now - 1 << endl;
            return;
        }
        if (a == 1)
        {
            now++;
            for (auto L : y)
                mm[L] = 1;
            continue;
        }
        bool flag = 0;
        for (auto L : y)
        {
            // cout << L << endl;
            string s1, s2;
            for (int i = 0; i < L.size() - 1; i++)
                s1 += L[i];
            for (int i = 1; i < L.size(); i++)
                s2 += L[i];
            if (mm[s1] && mm[s2])
            {
                flag = 1;
                mm[L] = 1;
            }
            // cout << a << endl;
            // cout << s1 << " " << s2 << endl;
        }
        if (!flag)
        {
            // cout << "this" << endl;
            cout << a - 1 << endl;
            return;
        }
        now++;
    }
    cout << now - 1 << endl;
}
// #define LOCAL
signed main()
{
    ios
    // fre
#ifdef LOCAL
        freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
    auto start = std::chrono::high_resolution_clock::now();
#endif

    int t = 1;
    // cin >> t;
    while (t--)
        solve();

#ifdef LOCAL
    auto end = std::chrono::high_resolution_clock::now();
    cout << "Execution time: "
         << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()
         << " ms" << '\n';
#endif
    return 0;
}