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#include <bits/stdc++.h>

using namespace std;


pair<int,int> BFS(int start, const vector<vector<int> >& Macierz, int n) {
    vector<bool> visited(n, false);
    vector<int> dys(n, INT_MAX);   
    queue<int> q;  

    
    visited[start] = true;
   dys[start] = 0; 
    q.push(start);

    int MaxDys = 0; 
    int NajdalszyNode = start; 

    while (!q.empty()) {
        int node = q.front();  
        q.pop(); 

        
        for (int i = 0; i < n; ++i) {
            
            if (Macierz[node][i] == 1 && !visited[i]) {
                visited[i] = true;  
                dys[i] = dys[node] + 1;  
                q.push(i);  

                
                if (dys[i] > MaxDys) {
                    MaxDys = dys[i];
                   NajdalszyNode = i;
                }}
            if (Macierz[node][i] == 2 && !visited[i]) {
                visited[i] = true;  
                dys[i] = dys[node];  
                q.push(i);  

                
                if (dys[i] > MaxDys) {
                    MaxDys = dys[i];
                   NajdalszyNode = i;
                }}
            }
        
    }


return {NajdalszyNode, MaxDys};


   
}

int main() {
	
	int t;
	cin>>t;
	for(int k=0;k<t;k++){
	
    int n;
    cin >> n;
    string s;
    vector<vector<int> > Macierz(n, vector<int>(n));

    for (int i = 0; i < n; ++i) {
    	cin>>s;
        for (int j = 0; j < n; ++j) {
            Macierz[i][j]=s[j]-'0';
        }
    }

    int start=0;
    pair<int, int> wynik = BFS(start, Macierz, n);

	int start2=wynik.first;

	wynik = BFS(start2, Macierz, n);

	Macierz[start2][wynik.first]=2;
	Macierz[wynik.first][start2]=2;
	
wynik = BFS(start, Macierz, n);
	cout<<wynik.second<<endl;
}
    return 0;
}