#include <bits/stdc++.h>

using namespace std;

int T;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> T;
    while (T--) {
        int n;
        cin >> n;
        string s, t;
        cin >> s >> t;
        int a, b, c;
        int p = 0;
        while (p < n && s[p] == t[p])p++;
        if (p == n) {
            cout << 1 << '\n';
            continue;
        }
        a = p;
        while (p < n && s[p] != t[p])p++;
        b = p - a;
        while (p < n && s[p] == t[p])p++;
        c = p - b;
        if (p == n) {
            cout << 2 * (a + b + c - 1) << '\n';
            continue;
        }
        while (p < n && s[p] != t[p])p++;
        while (p < n && s[p] == t[p])p++;
        if (p == n) {
            cout << 6 << '\n';
            continue;
        }
        cout << 0 << '\n';
    }
}