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

void solve()
{
    size_t n;
    string s, t;
    cin >> n;
    cin >> s >> t;
    bool flag = false;
    size_t cnt = 0;
    long long a[3] = {0, 0, 0};
    for (size_t i = 0; i < n; i++)
    {
        if (s[i] != t[i])
        {
            if (!flag)
            {
                cnt++;
                if (cnt >= 3)
                {
                    cout << "0\n";
                    return;
                }
                flag = true;
            }
            a[cnt]++;
        }
        else
        {
            flag = false;
        }
    }
    if (cnt == 1)
    {
        cout << 2 * (a[1] - 1) << '\n';
    }
    else
    {
        cout << 6 << '\n';
    }
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    size_t t;
    cin >> t;
    while (t--)
    {
        solve();
    }
}