#include <bits/stdc++.h>   using namespace std;   const int maxn = 1010;   string s[maxn];   int main() {     int n;     cin >> n;     for (int i = 1; i <= n; i++) cin >> s[i];     int ans = 6, cnt;     for (int i = 1; i <= n; i++) {       for (int j = i + 1; j <= n; j++) {         cnt = 0;         for (int k = 0; k < 6; k++)           if (s[i][k] != s[j][k]) cnt++;         ans = min(ans, (cnt + 1) / 2 - 1);       }     }     cout << ans;     return 0;   }   