#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
vector<vector<vector<int>>> pref;
map<char, int> mp;
int n;
void init(std::string a, std::string b) {
n = a.size();
pref.resize(a.size(), vector<vector<int>>(3, vector<int>(3,0)));
mp['T'] = 0; mp['A'] = 1; mp['C'] = 2;
for (int i = 0; i < a.size(); i++) {
if (i) pref[i] = pref[i-1];
pref[i][mp[a[i]]][mp[b[i]]]++;
}
}
int get_distance(int x, int y) {
int res = 0;
vector<vector<int>> vec = {{0,0,0},{0,0,0},{0,0,0}};
if (x) vec = pref[x-1];
auto vec2 = pref[y];
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) vec2[i][j] -= vec[i][j];
}
for (int i = 0; i < 3; i++) {
if (vec2[i][0] + vec2[i][1] + vec2[i][2] != vec2[0][i] + vec2[1][i] + vec2[2][i]) return -1;
}
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
if (i == j) continue;
int mini = min(vec2[i][j], vec2[j][i]);
res += mini;
vec2[i][j] -= mini;
vec2[j][i] -= mini;
}
}
res += (y-x+1 - res * 2) / 3 * 2;
return res;
}
