#include <bits/stdc++.h>
using namespace std;
//
#define ll long long
#define ull unsigned long long
#define mx 100010
#define mod 1000000007
#define inf INT_MAX
#define pi acos(-1.0)
#define endl '\n'
#define pb push_back
#define pll pair<ll, ll>
#define vll vector<ll>
#define vpll vector<pll>
#define Fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
//
int main() {
    ll t;
    cin >> t;

    while (t--) {
        ll n;
        cin >> n;

        string s, p;
        cin >> s >> p;

        vll charCount(200, 0);

        for (ll i = 0; i < s.length(); i++) {
            if (s[i] == '?' || p[i] == '?') {
                if (s[i] == p[i]) continue;
                ll x = p[i] - '0', y = s[i] - '0';
                //cout << x << " " << y << endl; //! test
                if (s[i] == '?') charCount[x]++;
                else charCount[y]++;
            }
        }

        ll charIdxV = 0, charIdxC = 0, tempV = 0, tempC = 0;
        for (ll i = 49; i <= 74; i++) {
            //cout << charCount[i] << " "; //! test
            if (tempV < charCount[i] && (i == 49 || i == 53 || i == 57 || i == 63 || i == 69)) {
                tempV = charCount[i];
                charIdxV = i;
            }
            else if (tempC < charCount[i] && (i != 49 && i != 53 && i != 57 && i != 63 && i != 69)) {
                tempC = charCount[i];
                charIdxC = i;
            }

        }

        ll countV = 0, countC = 0, countN = 0;
        bool cons = true, vow = true;
        string p1 = p, s1 = s;
        if (charIdxC != 0) charIdxC += 48;
        else charIdxC = 98;
        if (charIdxV != 0) charIdxV += 48;
        else charIdxV = 97;
        //cout << charIdxV << " " << charIdxC << endl; //! test
        for (ll i = 0; i < s.length(); i++) {

            if (s[i] == '?') s[i] = (char)charIdxV;
            if (p[i] == '?') p[i] = (char)charIdxV;
            //cout << s[i] << " " << p[i] << endl; //! test
            if (s[i] != p[i]) countV++;
            if ((s[i] != p[i]) && (s[i] == 'a' || s[i] == 'e' || s[i] == 'i' || s[i] == 'o' || s[i] == 'u') && (p[i] == 'a' || p[i] == 'e' || p[i] == 'i' || p[i] == 'o' || p[i] == 'u')) {
                countV++;
                //cout << "here" << endl; //! test
            }
            else if ((s[i] != p[i]) && (s[i] != 'a' && s[i] != 'e' && s[i] != 'i' && s[i] != 'o' && s[i] != 'u') && (p[i] != 'a' && p[i] != 'e' && p[i] != 'i' && p[i] != 'o' && p[i] != 'u')) countV++;

            if (s1[i] == '?') s1[i] = (char)charIdxC;
            if (p1[i] == '?') p1[i] = (char)charIdxC;
            if (s1[i] != p1[i]) countC++;
            if ((s1[i] != p1[i]) && (s1[i] != 'a' && s1[i] != 'e' && s1[i] != 'i' && s1[i] != 'o' && s1[i] != 'u') && (p1[i] != 'a' && p1[i] != 'e' && p1[i] != 'i' && p1[i] != 'o' && p1[i] != 'u')) countC++;
            else if ((s1[i] != p1[i]) && (s1[i] == 'a' || s1[i] == 'e' || s1[i] == 'i' || s1[i] == 'o' || s1[i] == 'u') && (p1[i] == 'a' || p1[i] == 'e' || p1[i] == 'i' || p1[i] == 'o' || p1[i] == 'u')) {
                countC++;
                //cout << "here" << endl; //! test
            }
        }

        //cout << countV << " " << countC << endl; //! test

        // if (charIdxV == 0 && cons == false) cout << countV << endl;
        // else if (charIdxC == 0 && vow == false) cout << countC << endl;
        // else if (!cons) cout << countV << endl;
        // else if (!vow) cout << countC << endl;
        // else cout << 0 << endl;
        //cout << "   " << countN << endl;
        cout << min(countV, countC) << endl;
    }

}