#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
using vi = vector<int>;
string ga, gb;
map<char, vi> prefixCharA, prefixCharB;
// prefix array of the positions where [c1][c2] c2 is in b instead of c1
map<char, map<char, int>> inPlaceOf[(int)1e5 + 1];
char characters[3] = {'A', 'T', 'C'};
void init(string a, string b)
{
int n = a.size();
ga = ' ' + a;
gb = ' ' + b;
for (char c : characters)
{
prefixCharA[c] = prefixCharB[c] = vi(n + 1, 0);
for (int i = 1; i <= n; i++)
{
prefixCharA[c][i] = (ga[i] == c) + prefixCharA[c][i - 1];
prefixCharB[c][i] = (gb[i] == c) + prefixCharB[c][i - 1];
}
}
for (int i = 1; i <= n; i++)
{
for (int j = 0; j < 3; j++)
for (int k = 0; k < 3; k++)
{
if (k == j)
continue;
inPlaceOf[i][characters[j]][characters[k]] =
inPlaceOf[i - 1][characters[j]][characters[k]];
}
if (ga[i] != gb[i])
inPlaceOf[i][ga[i]][gb[i]]++;
}
}
int get_distance(int x, int y)
{
x++, y++;
bool pos = true;
for (char c : characters)
{
int countInA = prefixCharA[c][y] - prefixCharA[c][x - 1];
int countInB = prefixCharB[c][y] - prefixCharB[c][x - 1];
pos &= (countInA == countInB);
}
if (!pos)
return -1;
map<char, map<char, int>> countIPO;
for (int j = 0; j < 3; j++)
for (int k = j + 1; k < 3; k++)
{
char c1 = characters[j], c2 = characters[k];
countIPO[c1][c2] = inPlaceOf[y][c1][c2] - inPlaceOf[x - 1][c1][c2];
countIPO[c2][c1] = inPlaceOf[y][c2][c1] - inPlaceOf[x - 1][c2][c1];
}
int moves = 0, leftover = 0;
for (int j = 0; j < 3; j++)
for (int k = j + 1; k < 3; k++)
{
char c1 = characters[j], c2 = characters[k];
int dif = min(countIPO[c1][c2], countIPO[c2][c1]);
countIPO[c1][c2] -= dif;
countIPO[c2][c1] -= dif;
moves += dif;
leftover += countIPO[c1][c2];
leftover += countIPO[c2][c1];
}
moves += 2 * leftover / 3;
return moves;
}
