#include <iostream>
#include <vector>
using namespace std;
const int ALPHABET_SIZE = 2;
struct node {
    node *children_of_this_node[ALPHABET_SIZE];
    bool end_of_word;
    
    node() {
        for(int i = 0; i < ALPHABET_SIZE; i++) {
            children_of_this_node[i] = NULL;
        }
        end_of_word = false;
    }
};
void insert_word(node * trie, string & s) {
    node * tmp = trie;
    for(int i = 0; i < (int) s.size(); i++) {
        int current_char = s[i] - 'a';
        if(tmp -> children_of_this_node[current_char] == NULL) {
            tmp -> children_of_this_node[current_char] = new node();
        }
        tmp = tmp -> children_of_this_node[current_char];
    }
    tmp -> end_of_word = true;
}
bool search_word(node * trie, string & s) {
    node * tmp = trie;
    for(int i = 0; i < (int) s.size(); i++) {
        int current_char = s[i] - 'a';
        if(tmp -> children_of_this_node[current_char] == NULL) {
            return false;
        }
        tmp = tmp -> children_of_this_node[current_char];
    }
    return tmp -> end_of_word;
}
int main() {
    ios_base::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<string> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }
    for(int i = 0; i < n; i++) {
        for(int j = i + 1; j < n; j++) {
            if((int) v[i].size() < (int) v[j].size()) {
                swap(v[i], v[j]);
            }
        }
    }
    node * tries[n - 1];
    for(int i = 0; i < n - 1; i++){
        tries[i] = new node();
    }
    for(int at = 1; at < n; at++) {
        for(int i = 0; i < (int) v[at].size(); i++) {
            string tmp = "";
            for(int j = i; j < min((int) i + 60, (int) v[at].size()); j++) {
                tmp += v[at][j];
                insert_word(tries[at - 1], tmp);
            }
        }
    }
    int result = 0;
    for(int i = 0; i < (int) v[0].size(); i++) {
        string tmp = "";
        for(int j = i; j < min(i + 60, (int) v[0].size()); j++) {
            tmp += v[0][j];
            bool ok = true;
            for(int k = 0; k < n - 1; k++) {
            
                if(!search_word(tries[k], tmp)) {
                    ok = false;
                    break;
                }
            }
            if(ok) {
                result = max(result, (int) tmp.size());
            }
        }
    }
    cout << result << endl;
    return 0;
}