#include <bits/stdc++.h>
#define ull unsigned long long
using namespace std;
int n;
int len[10];
string s[10];
ull BASE = 173;
ull bPow[2005];
ull hsh[10][2005];
set<ull> se[10];
bool check(int L)
{
    for (int i = 1; i <= n; i++)
        se[i].clear();
    for (int i = 1; i <= n - 1; i++)
    {
        for (int j = 1; j + L - 1 <= len[i]; j++)
        {
            ull nowHash = hsh[i][j + L - 1] - hsh[i][j - 1] * bPow[L];
            se[i].insert(nowHash);
        }
    }
    for (int j = 1; j + L - 1 <= len[n]; j++)
    {
        ull nowHash = hsh[n][j + L - 1] - hsh[n][j - 1] * bPow[L];
        bool flag = true;
        for (int k = 1; k <= n - 1; k++)
        {
            if (se[k].find(nowHash) == se[k].end())
            {
                flag = false;
                break;
            }
        }
        if (flag)
            return true;
    }
    return false;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> s[i];
        len[i] = s[i].size();
        s[i] = "^" + s[i] + "$";
    }
    // build Hash
    bPow[0] = 1;
    for (int i = 1; i <= 2000; i++)
        bPow[i] = bPow[i - 1] * BASE;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= len[i]; j++)
            hsh[i][j] = hsh[i][j - 1] * BASE + (s[i][j] - 'a' + 1);
    // bs
    int l = 0;
    int r = len[1];
    int ans = 0;
    while (l <= r)
    {
        int mid = (l + r) / 2;
        if (check(mid))
        {
            ans = mid;
            l = mid + 1;
        }
        else
        {
            r = mid - 1;
        }
    }
    cout << ans << endl;
    return 0;
}