#include "bits/stdc++.h"
using namespace std;
using ll = long long;
const ll inf = 1e9;
const int md1 = 1e9+7;
const int md2 = 998244353;
#define sz(v) ((int)v.size())
#define pb push_back
#define pry cout << "YES\n"
#define prn cout << "NO\n"
#define endl '\n'
#define fst first
#define scn second
/* #define ONPC */
struct sump {
int n;
vector<int> a;
vector<int> tr;
sump() {}
void
set(int _n) {
n = _n;
a.assign(n,0);
tr.assign(n,0);
}
void
add(int x)
{
++a[x];
return;
}
void
gen()
{
for (int i = 0; i < n; ++i) {
if (i) tr[i] = tr[i-1];
tr[i] += a[i];
}
return;
}
int
query(int x)
{
if (x < 0)
return 0;
return tr[x];
}
int
query(int l, int r)
{
return query(r) - query(l-1);
}
};
int n;
sump aa, at, ac;
sump ba, bt, bc;
sump t[6];
void
init(string a, string b)
{
n = sz(a);
aa.set(n);
at.set(n);
ac.set(n);
ba.set(n);
bt.set(n);
bc.set(n);
for (int i = 0; i < 6; ++i) t[i].set(n);
for (int i = 0; i < n; ++i) {
if (a[i] == 'A') {
aa.add(i);
if (b[i] == 'C') t[0].add(i);
if (b[i] == 'T') t[1].add(i);
}
if (a[i] == 'C') {
ac.add(i);
if (b[i] == 'A') t[2].add(i);
if (b[i] == 'T') t[3].add(i);
}
if (a[i] == 'T') {
at.add(i);
if (b[i] == 'A') t[4].add(i);
if (b[i] == 'C') t[5].add(i);
}
if (b[i] == 'A') ba.add(i);
if (b[i] == 'C') bc.add(i);
if (b[i] == 'T') bt.add(i);
}
return;
}
int
get_distance(int x, int y)
{
int v[6];
if (aa.query(x,y) != ba.query(x,y)) return 1;
if (ac.query(x,y) != bc.query(x,y)) return 1;
assert(at.query(x,y) == bt.query(x,y));
if (at.query(x,y) != bt.query(x,y)) return 1; /* USELESS */
for (int i = 0; i < 6; ++i) {
v[i] = t[i].query(x,y);
}
int ans = 0;
int a, b, c;
a = min(v[0], v[2]);
b = min(v[1], v[4]);
c = min(v[3], v[5]);
v[0] -= a;
v[2] -= a;
v[1] -= b;
v[4] -= b;
v[3] -= c;
v[5] -= c;
ans = a + b + c;
ans += (v[0]<<1);
ans += (v[1]<<1);
return ans;
}
#ifdef ONPC
void
solve()
{
}
int32_t
main(int argc, char **argv)
{
if (argc >= 2) {
freopen(argv[1], "r", stdin);
} else
ios_base::sync_with_stdio(0);cin.tie(0);
int t = 1;
/* cin >> t; */
while(t--)
solve();
}
#endif
