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#include <bits/stdc++.h>
using namespace std;


typedef long long ll;
typedef unsigned long long ull;
typedef long double lld;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvll;
typedef vector<vector<int>> vvi;
typedef pair<ll, ll> pll;
ll mod = 1e9+7 ;
void solve() {
    int n;
    cin>>n;
    char grid[2][n];
    set<int>s;
    for (int i=0;i<2;++i) {
        for (int j = 0; j < n; j++) {
            cin >> grid[i][j];
            if (grid[i][j] == '.')s.insert(j);
        }
    }
        int output=0;
        if (s.empty()) {
            cout<<0<<endl;
            return;
        }
        for (int i=1;i<n-1;++i) {
            if (grid[0][i]=='x')continue;
            if (grid[1][i]=='x')continue;
            if (grid[0][i-1]=='.' && grid[1][i-1]=='.')continue;
            if (grid[0][i+1]=='.' && grid[1][i+1]=='.')continue;
            if ((grid[0][i-1]=='x' && grid[0][i+1]=='x') || (grid[1][i-1]=='x' && grid[1][i+1]=='x')) {
                if (*s.begin() < i && *(--s.end()) > i) {
                    output++;
                }
            }
        }
        cout<<output<<endl;
    }



int main() {
    int t;
    cin>>t;
    while(t--)
        solve();
    return 0;
}