#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
map<char, int> mp;
string a, b;
const int MAXN = 1e5;
int tot[MAXN][3][3], tbal[MAXN][3], same[MAXN];
void init(std::string _a, std::string _b) {
a = _a;
b = _b;
mp['A'] = 0;
mp['T'] = 1;
mp['C'] = 2;
int n = a.size();
for (int i = 0; i < n; ++i) {
int ai = mp[a[i]];
int bi = mp[b[i]];
tbal[i][ai] += 1;
tbal[i][bi] -= 1;
tot[i][ai][bi] += 1;
same[i] = (ai == bi);
if (i) {
for (int j = 0; j < 3; ++j) {
tbal[i][j] += tbal[i - 1][j];
}
for (int j = 0; j < 3; ++j) {
for (int k = 0; k < 3; ++k) {
tot[i][j][k] += tot[i - 1][j][k];
}
}
same[i] += same[i - 1];
}
}
}
// 1, 2, 4
// 8, 16, 32
int get_distance(int x, int y) {
vector<vector<int>> cnt(3, vector<int>(3));
vector<int> bal(3);
int res = 0;
for (int i = 0; i < 3; ++i) {
bal[i] = tbal[y][i] - (x - 1 >= 0 ? tbal[x - 1][i] : 0);
}
for (int i = 0; i < 3; ++i) {
for (int j = 0; j < 3; ++j) {
cnt[i][j] = tot[y][i][j] - (x - 1 >= 0 ? tot[x - 1][i][j] : 0);
}
}
int left = y - x + 1 - (same[y] - (x - 1 >= 0 ? same[x - 1] : 0));
for (int i = 0; i < 3; ++i) {
for (int j = 0; j < 3; ++j) {
int take = min(cnt[i][j], cnt[j][i]);
cnt[i][j] -= take;
cnt[j][i] -= take;
left -= 2 * take;
res += take;
}
}
for (auto& i : bal) {
if (i != 0) return -1;
}
// cerr << "[" << a.substr(x, y - x + 1) << " , " << b.substr(x, y - x + 1) << "] = " << res << "\n";
// assert(res % 2 == 0);
// cerr << left << "\n";
// assert(left % 3 == 0);
return res + (left / 3) * 2;
}
