#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Vi = vector<int>;
using Pii = pair<int,int>;
#define mp make_pair
#define pb push_back
#define x first
#define y second
#define rep(i,b,e) for(int i = (b); i < (e); i++)
#define each(a, x) for(auto& a : (x))
#define all(x) (x).begin(),(x).end()
#define sz(x) int((x).size())

#define tem template<class t,class u,class...w>
#define pri(x,y)tem auto operator<<(t& o, u a)->decltype(x,o) { o << y; return o; }
pri(a.print(), "{"; a.print(); "}");
pri(a.y, "(" << a.x << ", " << a.y << ")");
pri(all(a), "["; auto d=""; for (auto i : a) (o << d << i, d = ", "); o << "]");
void DD(...) {}
tem void DD(t s, u a, w... k) {
	for (int b = 44; *s && *s - b; cerr << *s++)
		b += ((*s == 41) - (*s == 40)) * 88;
	cerr << ": " << a << *s++; DD(s, k...);
}
tem vector<t> span(const t* a, u n) { return {a, a+n}; }
#ifdef LOC
#define deb(...) (DD("[,\b :] "#__VA_ARGS__, __LINE__, __VA_ARGS__), cerr << endl)
#else
#define deb(...)
#endif
#define DBP(...) void print() { DD(#__VA_ARGS__, __VA_ARGS__); }

int mat[4][4];

int get(char c) {
	if (c == 'A') return 0;
	if (c == 'C') return 1;
	if (c == 'G') return 2;
	return 3;
}

int main() {
	cin.sync_with_stdio(0); cin.tie(0);
	cout << fixed << setprecision(12);

	string s, t; cin >> s >> t;
	int n = sz(s);

	ll ans = 0;

	rep(i, 0, n) {
		int a = get(s[i]), b = get(t[i]);
		mat[a][b]++;
	}

	rep(len, 1, 5) {
		Vi perm(4);
		iota(all(perm), 0);

		do {
			int sm = INT_MAX;
			rep(i, 0, len) {
				sm = min(sm, mat[perm[i]][perm[(i+1)%len]]);
			}
			ans += sm*ll(len-1);
			rep(i, 0, len) {
				mat[perm[i]][perm[(i+1)%len]] -= sm;
			}
		} while (next_permutation(all(perm)));
	}

	cout << ans << endl;
	return 0;
}