#include <bits/stdc++.h>
using namespace std;
 
int main() {
	// your code goes here
	int q,r; cin >> q;
	for(r=0;r<q;r++){
		int n,i,j,m[200005],a[5][5]={0},ans,sum;
		vector<int> v[200005],c,d;
		cin >> n;
		for(i=0;i<n;i++){
			char s[4000005];
			cin >> s;
			m[i]=strlen(s);
			for(j=0;j<m[i];j++) v[i].push_back(s[j]-'0');
			a[v[i][0]][v[i][m[i]-1]]++;
			if(v[i][0]==0&&v[i][m[i]-1]==1) c.push_back(i);
			if(v[i][0]==1&&v[i][m[i]-1]==0) d.push_back(i);
		}
		if(n==1){
			cout << "0" << endl << endl;
			continue;
		}
		if(a[1][0]==0&&a[0][1]==0&&a[0][0]>0&&a[1][1]>0){
			cout << "-1" << endl;
			continue;
		}
		sum=a[0][1]+a[1][0];
		if(sum%2==0) ans=max(a[0][1],a[1][0])-sum/2;
		else ans=max(a[0][1],a[1][0])-(sum+1)/2;
 
 
	}
	return 0;
}

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