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#include <bits/stdc++.h>

using namespace std;

int n;
int inf = 401;
int dp[400][400];
bitset<400> dpb[400];
bitset<400> b[403];

bool check(int length)
{
    // cout << length << '\n';
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < n; ++j)
        {
            if (dp[i][j] > length) dpb[i][j] = true;
            else dpb[i][j] = false;
        }
    }
    for (int l = 0; l < n - 1; ++l)
    {
        for (int r = l + 1; r < n; ++r)
        {
            bool ok = true;
            for (int i = 0; i < n; ++i)
            {
                int v = min(dp[i][l], dp[i][r]);
                b[v][i] = true;
            }
            for (int i = inf - 1; i >= 0; --i)
            {
                b[i] = b[i] | b[i + 1];
            }
            for (int i = 0; i < n - 1; ++i)
            {
                int v = min(dp[i][l], dp[i][r]);
                if (v > length)
                {
                    if (dpb[i].any())
                    {
                        ok = false;
                        break;
                    }
                }
                else if ((dpb[i] & b[length - v + 1]).any())
                {
                    ok = false;
                    break;
                }
            }
            for (int i = 0; i <= inf; ++i) b[i].reset();
            if (ok) return true;
        }
    }
    return false;
}

void solve()
{
    cin >> n;
    
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < n; ++j)
        {
            char c;
            cin >> c;
            if (c == '1')
                dp[i][j] = 1;
            else
                dp[i][j] = inf;
        }
    }

    for (int i = 0; i < n; ++i) dp[i][i] = 0;

    for (int k = 0; k < n; ++k)
    {
        for (int i = 0; i < n; ++i)
        {
            for (int j = 0; j < n; ++j)
            {
                dp[i][j] = min(dp[i][j], dp[i][k] + dp[k][j]);
            }
        }
    }

    int l = 0, r = inf;

    while (l < r)
    {
        int m = (l + r) / 2;

        if (check(m))
            r = m;
        else
            l = m + 1;
    }
    
    if (r >= inf) cout << "-1\n";
    else cout << r << '\n';

    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < n; ++j)
            dp[i][j] = 0;
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int t;
    cin >> t;

    for (int i = 0; i < t; ++i)
        solve();
}