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#include <iostream>
#include <vector>
#include <string>
using namespace std;
const int alphabet_size = 2;
struct node {
    node * children_of_node[alphabet_size];
    bool is_end_of_word;
    node () {
        is_end_of_word = false;
        for(int i = 0; i < alphabet_size; i++) {
            children_of_node[i] = NULL;
        }
    }
};
void insert_word(node * trie, string word) {
    node * tmp = trie;
    for(int i = 0; i < (int) word.size(); i++) {
        int c = word[i] - 'a';
        if(tmp -> children_of_node[c] == NULL) {
            tmp -> children_of_node[c] = new node();
        }
        tmp = tmp -> children_of_node[c];
    }
    tmp -> is_end_of_word = true;
}
bool search_word(node * trie, string word) {
    node * tmp = trie;
    
    for(int i = 0; i < (int) word.size(); i++) {
        int c = word[i] - 'a';
        if(tmp -> children_of_node[c] == NULL) {
            return false;
        }
        tmp = tmp -> children_of_node[c];
    }
    return tmp -> is_end_of_word;
}
void delete_word(node * trie, string word) {
    node * tmp = trie;
    for(int i = 0; i < (int) word.size(); i++) {
        int c = word[i] - 'a';
        if(tmp -> children_of_node[c] == NULL) {
            return;
        }
        tmp = tmp -> children_of_node[c];
    }
    tmp -> is_end_of_word = false;
}

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 * trie[n + 1];
    for(int i = 0; i < n; i++) {
        trie[i] = new node();
    }
    for(int i = 1; i < n; i++) {
        for(int j = 0; j < (int) v[i].size(); j++) {
            string tmp = "";
            for(int k = j; k < min(j + 60, (int) v[i].size()); k++) {
                tmp += v[i][k];
                insert_word(trie[i], tmp);
            }
        }
    }
    int res = 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 = 1; k < n; k++) {
                if(!search_word(trie[k], tmp)) {
                    ok = false;
                    break;
                }
            }
            if(ok) {
                res = max(res, (int) tmp.size());
            }
        }
    }
    cout << res << endl;
    return 0;
}