#include <iostream>
#include <vector>

using namespace std;

int main()
{
    unsigned int t, n, min = INT16_MAX;
    cin >> t;
    for (int i = 0; i < t; i++)
    {
        cin >> n;
        vector<unsigned int> vec(n);
        for (int j = 0; j < n; j++)
        {
            cin >> vec.at(j);
            for (int k = 0; k < j; k++)
                if ((vec[k] ^ vec[j]) < min)
                    min = vec[k] ^ vec[j];
        }
    }
    cout << min;
}