#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int INF = 1e9;
const int MOD = 1e9 + 7;
int n, p1[100002], p2[100002];
struct nod {
int fr[4];
int cnt[4][4];
nod () {
memset(fr, 0, sizeof(fr));
memset(cnt, 0, sizeof(cnt));
}
} aint[400002];
nod merge (nod st, nod dr) {
nod ans;
for (int i = 1; i <= 3; i++)
ans.fr[i] = st.fr[i] + dr.fr[i];
for (int i = 1; i <= 3; i++)
for (int j = 1; j <= 3; j++)
ans.cnt[i][j] += st.cnt[i][j] + dr.cnt[i][j];
return ans;
}
void build (int nod, int st, int dr) {
if (st == dr) {
aint[nod].fr[p1[st]]++;
aint[nod].fr[p2[st]]--;
aint[nod].cnt[p1[st]][p2[st]]++;
return;
}
int mij = (st + dr) / 2;
build(2 * nod, st, mij);
build(2 * nod + 1, mij + 1, dr);
aint[nod] = merge(aint[2 * nod], aint[2 * nod + 1]);
}
nod query(int nod, int st, int dr, int a, int b) {
if (a <= st && dr <= b) {
return aint[nod];
}
int mij = (st + dr) / 2;
if (b <= mij)
return query(2 * nod, st, mij, a, b);
else if (a > mij)
return query(2 * nod + 1, mij + 1, dr, a, b);
else
return merge(query(2 * nod, st, mij, a, b), query(2 * nod + 1, mij + 1, dr, a, b));
}
void init (string a, string b) {
n = a.size();
map<char, int>mp;
mp['A'] = 1;
mp['C'] = 2;
mp['T'] = 3;
for (int i = 1; i <= n; i++) {
p1[i] = mp[a[i - 1]];
p2[i] = mp[b[i - 1]];
}
build(1, 1, n);
}
int get_distance (int x, int y) {
x++;y++;
nod ans = query(1, 1, n, x, y);
if (ans.fr[1] != 0 || ans.fr[2] != 0 || ans.fr[3] != 0)
return -1;
int cycles = 0;
int sz = y - x + 1;
cycles += ans.cnt[1][1];
cycles += ans.cnt[2][2];
cycles += ans.cnt[3][3];
sz -= cycles;
cycles += min(ans.cnt[1][2], ans.cnt[2][1]);
sz -= 2 * min(ans.cnt[1][2], ans.cnt[2][1]);
cycles += min(ans.cnt[1][3], ans.cnt[3][1]);
sz -= 2 * min(ans.cnt[1][3], ans.cnt[3][1]);
cycles += min(ans.cnt[2][3], ans.cnt[3][2]);
sz -= 2 * min(ans.cnt[2][3], ans.cnt[3][2]);
cycles += sz / 3;
return y - x + 1 - cycles;
}
