#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e5 + 5;
int same[N];
int n;
vector<int> wa[3], wb[3];
map<string, vector<int>> mp;
int get_range(const vector<int>& vec, int l, int r){
return upper_bound(vec.begin(), vec.end(), r) - lower_bound(vec.begin(), vec.end(), l);
}
void init(std::string a, std::string b) {
n = a.size();
for (int i = 0; i < n; i++) same[i] = (a[i] == b[i]);
for (int i = 0; i < n; i++) same[i] += same[i-1];
for (int i = 0; i < n; i++){
if (a[i] == 'A') wa[0].push_back(i);
else if (a[i] == 'C') wa[1].push_back(i);
else wa[2].push_back(i);
}
for (int i = 0; i < n; i++){
if (b[i] == 'A') wb[0].push_back(i);
else if (b[i] == 'C') wb[1].push_back(i);
else wb[2].push_back(i);
}
for (int i = 0; i < n; i++){
string s; s.append(1, a[i]); s.append(1, b[i]);
mp[s].push_back(i);
}
}
int get_distance(int x, int y) {
bool ok = true;
for (int i = 0; i < 3; i++){
int c1 = get_range(wa[i], x, y);
int c2 = get_range(wb[i], x, y);
if (c1 != c2) {ok = false; break;}
}
if (!ok) return -1;
int len = y-x+1, ans = 0, res;
res = min(get_range(mp["AC"], x, y), get_range(mp["CA"], x, y)); ans += res; len -= 2 * res;
res = min(get_range(mp["AT"], x, y), get_range(mp["TA"], x, y)); ans += res; len -= 2 * res;
res = min(get_range(mp["CT"], x, y), get_range(mp["TC"], x, y)); ans += res; len -= 2 * res;
int s = (same[y] - ((x-1 < 0)? 0: same[x-1]));
len -= s;
return ans + len/3*2;
}
