#include <vector>
#include <string>
#include <algorithm>
using namespace std;
// Prefiks yig'indilari uchun 2D massivlar
// cnt[tur][index] - 6 xil farqli juftliklar sonini saqlaydi
// char_cnt[belgi][index] - har bir belgining sonini saqlaydi
int pref[6][100005];
int c_pref[3][100005]; // 0:A, 1:T, 2:C
void init(string a, string b) {
int n = a.length();
for (int i = 0; i < n; i++) {
// Avvalgi yig'indilarni ko'chirish
for (int j = 0; j < 6; j++) pref[j][i + 1] = pref[j][i];
for (int j = 0; j < 3; j++) c_pref[j][i + 1] = c_pref[j][i];
// Belgilar sonini sanash
if (a[i] == 'A') c_pref[0][i + 1]++;
else if (a[i] == 'T') c_pref[1][i + 1]++;
else c_pref[2][i + 1]++;
if (b[i] == 'A') c_pref[0][i + 1]--;
else if (b[i] == 'T') c_pref[1][i + 1]--;
else c_pref[2][i + 1]--;
// Juftliklarni aniqlash (faqat farqli bo'lsa)
if (a[i] != b[i]) {
if (a[i] == 'A' && b[i] == 'T') pref[0][i + 1]++;
else if (a[i] == 'A' && b[i] == 'C') pref[1][i + 1]++;
else if (a[i] == 'T' && b[i] == 'A') pref[2][i + 1]++;
else if (a[i] == 'T' && b[i] == 'C') pref[3][i + 1]++;
else if (a[i] == 'C' && b[i] == 'A') pref[4][i + 1]++;
else if (a[i] == 'C' && b[i] == 'T') pref[5][i + 1]++;
}
}
}
int get_distance(int x, int y) {
// 1. Belgilar soni tengligini tekshirish
for (int i = 0; i < 3; i++) {
if (c_pref[i][y + 1] - c_pref[i][x] != 0) return -1;
}
// 2. Juftliklar miqdorini olish
int AT = pref[0][y + 1] - pref[0][x];
int AC = pref[1][y + 1] - pref[1][x];
int TA = pref[2][y + 1] - pref[2][x];
int TC = pref[3][y + 1] - pref[3][x];
int CA = pref[4][y + 1] - pref[4][x];
int CT = pref[5][y + 1] - pref[5][x];
int res = 0;
// To'g'ridan-to'g'ri almashtirishlar (masalan, AT va TA)
int m;
m = min(AT, TA); res += m; AT -= m; TA -= m;
m = min(AC, CA); res += m; AC -= m; CA -= m;
m = min(TC, CT); res += m; TC -= m; CT -= m;
// Siklli almashtirishlar (qolgan juftliklar 3-lik sikl hosil qiladi)
// Har bir sikl 2 ta almashtirish talab qiladi
res += (AT + AC + TA + TC + CA + CT) / 3 * 2;
return res;
}
