#include <iostream>
#include <vector>
#include <string>
using namespace std;

int main()
{
	int Ncas;

	cin >> Ncas;
	
	for(int i = 0; i < Ncas; i++)
	{ 
		int N ; //longueur d'une paire descalier
		cin >> N;

		vector <char> TabEscalier1; // contient val du dés
		char valEscalier1;

		for(int j = 0; j < N; j++)
		{
			
			cin >> valEscalier1;

			TabEscalier1.push_back(valEscalier1);


		}
		


		vector <char> TabEscalier2; // contient val du dés
		char valEscalier2;

		for(int j = 0; j < N; j++)
		{

			cin >> valEscalier2;

			TabEscalier2.push_back(valEscalier2);
			

		}

 		


  		reverse(TabEscalier2.begin(), TabEscalier2.end());




  		int count = 0;

  		for(int j = 0; j < N; j++)
		{
			if(TabEscalier1[j] == '1' &&  TabEscalier2[j] == '1')
				count++; 

		}

		cout << count << endl;



		
	}
	


	return 0;

}