#define _CRT_SECURE_NO_WARNINGS
#define debug(l) cerr<<#l<<' '<<l<<'\n';
#include "bits/stdc++.h"
using namespace std;
#define all(pref) pref.begin(), pref.end()
typedef long long ll;
typedef pair<ll, ll> pll;
typedef long double ld;
signed main() {
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    const ll inf = 1e18;
    ll t;
    cin >> t;
    while (t--) {
        ll n;
        cin >> n;
        vector<string> a(2);
        cin >> a[0];
        cin >> a[1];
        pll f, l;
        for (ll i = 0; i < n; i++) {
            bool fl = false;
            for (ll j = 0; j < 2; j++) {
                if (a[j][i] == '*') {
                    f = { j,i };
                    fl = true;
                    break;
                }
            }
            if (fl)break;
        }
        for (ll i = n-1; i>=0; i--) {
            bool fl = false;
            for (ll j = 0; j < 2; j++) {
                if (a[j][i] == '*') {
                    l = { j,i };
                    fl = true;
                    break;
                }
            }
            if (fl)break;
        }
        vector<vector<ll>> dp(2, vector<ll>(n, 0));
        for (ll i = f.second; i <= l.second; i++) {
            if (i > 0 && i!=f.second) {
                dp[1][i] = dp[1][i - 1] + 1;
                dp[0][i] = dp[0][i - 1] + 1;
                dp[1][i] = min(dp[1][i], dp[0][i] + 1);
                dp[0][i] = min(dp[0][i], dp[1][i] + 1);
            }
            if (a[0][i] == '*') {
                if (a[1][i] == '*') {
                    dp[0][i] = min(dp[1][i] + 1, dp[0][i] + 1);
                    dp[1][i] = dp[0][i];
                }
                else {
                    dp[1][i]++;
                }

            }
            else if (a[1][i] == '*') {
                dp[0][i]++;
            }
        }
        cout << dp[l.first][l.second] << '\n';

    }

}