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

using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    auto solve = [&]() {
        int n;
        cin >> n;

        vector<string> s(n);
        for (int i = 0; i < n; i++) {
            cin >> s[i];
        }

        set<string> cand;

        for (int i = 0; i < int(s[0].size()); i++) {
            for (int j = 1; i + j <= int(s[0].size()); j++) {
                cand.emplace(s[0].substr(i, j));
            }
        }

        int ans = 0;

        for (auto t : cand) {
            bool ok = true;
            for (int i = 1; i < n; i++) {
                if (s[i].find(t) == -1) {
                    ok = false;
                    break;
                }
            }
            if (ok) {
                ans = max(ans, int(t.size()));
            }
        }

        cout << ans << '\n';
    };
    
    solve();
    
    return 0;
}