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

vector <int> tab[4][4];
string a, b;

bool test(int i) {
    return a[i] == b[i];
}

bool is(vector <int> t, int x) {
    for (int i = 0; i < (int)t.size(); ++i) {
        if (t[i] == x) return true;
    }
    return false;
}

int main() {
    

    cin >> a >> b;

    for (int i = 0; i < (int)a.size(); ++i) {
        if (a[i] == 'A') a[i] = 0;
        if (a[i] == 'C') a[i] = 1;
        if (a[i] == 'G') a[i] = 2;
        if (a[i] == 'T') a[i] = 3;

        if (b[i] == 'A') b[i] = 0;
        if (b[i] == 'C') b[i] = 1;
        if (b[i] == 'G') b[i] = 2;
        if (b[i] == 'T') b[i] = 3;
    }

    for (int i = 0; i < (int)a.size(); ++i) {
        tab[a[i]][b[i]].push_back(i);
    }

    /*for (int i = 0; i < 4; ++i) {
        for (int j = 0; j < 4; ++j) {
            cout << i << " " << j << ": " << tab[i][j].size() << endl;
        }
    }*/

    /*int answer = 0;
    for (int i = 0; i < (int)a.size(); ++i) {
        if (!test(i)) {
            while (!tab[b[i]][a[i]].empty()) {
                int x = tab[b[i]][a[i]].back();

                if (test(x)) {
                    tab[b[i]][a[i]].pop_back();
                }
                else {
                    swap(a[i], a[x]);
                    tab[b[i]][a[i]].pop_back();
                    break;
                }
            }
        }
    }*/

    queue <vector <int> > que;
    vector <int> tmp;
    tmp.push_back(0);
    
    for (int i = 0; i < 4; ++i) {
        tmp[0] = i;
        que.push(tmp);
    }

    int answer = 0;
    while (!que.empty()) {
        auto T = que.front(); que.pop();
        //cout << T.size() << endl;

        for (int i = 0; i < 4; ++i) {
            if (i == T[0]) {
                /*if (T.size() == 2 && T[0] == 2 && T[1] == 3) {
                    for (int i = 0; i < 4; ++i) {
                        for (int j = 0; j < 4; ++j) {
                            cout << i << " " << j << ": " << tab[i][j].size() << endl;
                        }
                    }
                }*/


                //cout << tab[T.back()][T[0]].size() << endl;
                int x = tab[T.back()][T[0]].size();
                for (int j = 0; j < (int)T.size()-1; ++j) {
                    x = min(x, (int)tab[T[j]][T[j+1]].size());
                    //cout << T[j] << " " << T[i+1] << " " << tab[T[i]][T[i+1]].size() << endl;
                }
                
                for (int j = 0; j < (int)T.size()-1; ++j) {
                    int X = x;
                    while (X--) {
                        tab[T[j]][T[j+1]].pop_back();
                    }
                }
                int X = x;
                while (X--) {
                    tab[T.back()][T[0]].pop_back();
                }
                answer += ((int)T.size() - 1) * x;

                /*cout << x << ": ";
                for (int k = 0; k < T.size(); ++k) cout << T[k];
                cout << endl;*/
            }
            if (!is(T, i)) {
                tmp = T;
                tmp.push_back(i);
                que.push(tmp);
            }
        }
    }

    printf("%d\n", answer);


}