#include <iostream>
#include <string>
#include <string.h>
#include <vector>
#include <algorithm>
#include <cmath>
#include <set>
#include <random>
#include <cstdlib>
#include <numeric>
#include <functional>
#include <queue>
using namespace std;
using ll = long long;
ll mod = 1e9 + 7;

void slove()
{
	int n;
	cin >> n;

	string s(n + 1 , 0), t(n + 1,0);

	for (int i = 1; i <= n; i++)
		cin >> s[i];
	for (int i = 1; i <= n; i++)
		cin >> t[i];

	vector<int> tmp(n + 1, 0);
	for (int i = 1; i <= n; i++)
		if (s[i] != t[i])
			tmp[i] = 1;
	vector<pair<int, int>> data;
	// 处理为连续的区间

	for (int i = 1; i <= n; i++)
	{
		if (tmp[i] == 1)
		{
			int j = i;
			while (j + 1 <= n && tmp[j + 1] == 1)
				j++;

			data.emplace_back(i, j);
			i = j;
		}
	}

	if (data.size() > 2)
	{
		cout << 0 << endl;
		return;
	}
	else if (data.size() == 2)
	{
		cout << 6 << endl;
	}
	else
	{
		int ans = n - (data[0].second - data[0].first + 1);
		ans += (data[0].second - data[0].first);
		ans *= 2;
		cout << ans << endl;
	}
	return;

}

int main()
{
    //freopen("out.txt", "w", stdout);
    //freopen("in.txt", "r", stdin);
    ios::sync_with_stdio(false);

    cin.tie(0);
    cout.tie(0);

    int cnt = 1;
    cin >> cnt;

    while (cnt--)
    {
        slove();
    }
};