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#include <bits/stdc++.h>
using namespace std;
int n, t, maxx, pier, drug, ile, ile2, sum;
string s;
int kra[407][407], kra2[4007][4007];

vector<int> wyn;
int main()
{

    cin >> t;

    while(t--)
    {
        cin >> n;  maxx = 1e5;
        for(int i = 1; i <= n; i++)
        {
            cin >> s;
            for(int y = 0; y < s.size(); y++)
            {
                if(i == y+1)
                {
                    kra[i][y+1] = 0;
                }
                else if(s[y] == '0')
                {
                    kra[i][y+1] = 1e9; kra[y+1][i] = 1e9;
                }
                else
                {
                    kra[i][y+1] = 1; kra[y+1][i] = 1;
                }
            }
        }

        for(int i = 1; i <= n; i++)
        {
            for(int v = 1; v <= n; v++)
            {
                for(int u = 1; u <= n; u++)
                {
                    if(kra[v][i] + kra[i][u] < kra[v][u])
                    {
                        kra[v][u] = kra[v][i] + kra[i][u];
                        kra[u][v] = kra[v][i] + kra[i][u]; // i wtedy mamy najszybsza sicezke
                    }
                }
            }
        }

        for(int i = 1; i <= n; i++)
        {
            for(int y = 1; y <= n; y++)
            {
                kra2[i][y] = kra[i][y];
            }
        }

        for(int a = 1; a <= n; a++)
        {
            for(int b = 1; b <= n; b++)
            {
                kra2[a][b] = 0; kra2[b][a] = 0;
                for(int i = 1; i <= n; i++)
                {
                    for(int v = 1; v <= n; v++)
                    {
                        for(int u = 1; u <= n; u++)
                        {
                            if(kra2[v][i] + kra2[i][u] < kra2[v][u])
                            {
                                kra2[v][u] = kra2[v][i] + kra2[i][u];
                                kra2[u][v] = kra2[v][i] + kra2[i][u];  // i wtedy mamy najszybsza sicezke
                            }
                        }
                    }
                }

                sum = -5;
                for(int i = 1; i <= n; i++)
                {
                    for(int y = 1; y <= n; y++)
                    {
                       if(kra2[i][y] > sum)
                       {
                            sum = kra2[i][y];
                       }
                        kra2[i][y] = kra[i][y];
                    }
                }
              //  cout << " a " << a << " b " << b << " sum " << sum << endl;
                maxx = min(sum, maxx);
            }
        }

        wyn.push_back(maxx);
    }


    for(int i = 0; i < wyn.size(); i++)
    {
        cout << wyn[i] << '\n';
    }





}