#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
#define arr array
#define hmap unordered_map
#define mp make_pair
#define fir first
#define sec second
const int N = 1e5 + 5;
int n;
arr<char, N> a, b;
hmap<string, arr<int, N>> sm;
void sm_cmp() {
for (int i = 1; i <= n; i++) {
string x = "";
x += a[i], x += b[i];
for (string y : {"AA", "AC", "AT", "CC", "CA", "CT", "TT", "TA", "TC"}) {
sm[y][i] = sm[y][i - 1] + (x == y);
}
}
// for (int i = 1; i <= n; i++)
// cout << i << ": " << sm["AT"][i] << '\n';
}
void init(string _a, string _b) {
n = _a.size();
for (int i = 1; i <= n; i++)
a[i] = _a[i - 1], b[i] = _b[i - 1];
sm_cmp();
}
int get_distance(int l, int r) {
l++, r++;
hmap<string, int> cnt;
for (string x : {"AC", "AT", "CA", "CT", "TA", "TC"}) {
cnt[x] = sm[x][r] - sm[x][l - 1];
}
if (cnt["AT"] + cnt["AC"] != cnt["TA"] + cnt["CA"]) return -1;
if (cnt["CT"] + cnt["CA"] != cnt["AC"] + cnt["TC"]) return -1;
int ans = 0;
for (pair<string, string> x : {mp("AT", "TA"), mp("AC", "CA"), mp("CT", "TC")}) {
int rmv = min(cnt[x.fir], cnt[x.sec]);
ans += rmv, cnt[x.fir] -= rmv, cnt[x.sec] -= rmv;
}
int mx = 0;
for (string x : {"AC", "AT", "CA", "CT", "TA", "TC"}) {
mx = max(mx, cnt[x]);
}
ans += 2 * mx;
return ans;
}
