#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 1;
int p[3][N] = {}, pre[3][3][N] = {};
void init(std::string a, std::string b) {
int n = a.size();
string t = "ATC";
for (int i = 0; i < n; i++)
{
for (int j = 0; j < 3; j++) p[j][i + 1] += p[j][i];
int f = t.find(a[i]);
p[f][i + 1]++;
int s = t.find(b[i]);
p[s][i + 1]--;
for (int j = 0; j < 3; j++)
{
for (int k = 0; k < 3; k++)
{
pre[j][k][i + 1] += pre[j][k][i];
}
}
if (f != s) pre[f][s][i + 1]++;
}
}
int get_distance(int x, int y) {
for (int i = 0; i < 3; i++)
{
if (p[i][y + 1] != p[i][x]) return -1;
}
int a[3][3] = {};
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
a[i][j] = pre[i][j][y + 1] - pre[i][j][x];
}
}
int ans = 0, rem = 0;
for (int i = 0; i < 3; i++)
{
for (int j = i + 1; j < 3; j++)
{
int k = min(a[i][j], a[j][i]);
ans += k;
a[i][j] -= k;
a[j][i] -= k;
}
}
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++) rem += a[i][j];
}
assert(rem % 3 == 0);
return ans + rem / 3 * 2;
}
