#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
constexpr int N = 1E5 + 4;
int n;
int A[N];
int B[N];
int pre[N][3][3];
int cnt[3][3];
void fill_with(int l, int r) {
memset(cnt, 0, sizeof cnt);
for (int x = 0; x < 3; x++) for (int y = 0; y < 3; y++) cnt[x][y] = pre[r+1][x][y] - pre[l][x][y];
}
void init(std::string a, std::string b) {
n = a.size();
for (int i = 0; i < n; i++) {
if (a[i] == 'A') A[i]=0;
if (a[i] == 'C') A[i]=1;
if (a[i] == 'T') A[i]=2;
}
for (int i = 0; i < n; i++) {
if (b[i] == 'A') B[i]=0;
if (b[i] == 'C') B[i]=1;
if (b[i] == 'T') B[i]=2;
}
for (int i = 0; i < n; i++) {
for (int x = 0; x < 3; x++) for (int y = 0; y < 3; y++) pre[i + 1][x][y] = pre[i][x][y];
pre[i + 1][A[i]][B[i]]++;
}
}
int get_distance(int x, int y) {
fill_with(x, y);
if (cnt[0][1] + cnt[0][2] != cnt[1][0] + cnt[2][0]) return -1;
if (cnt[1][0] + cnt[1][2] != cnt[0][1] + cnt[2][1]) return -1;
if (cnt[2][0] + cnt[2][1] != cnt[0][2] + cnt[1][2]) return -1;
int ans=0;
int t = min(cnt[0][1], cnt[1][0]);
cnt[0][1] -= t; cnt[1][0] -= t; ans += t;
t = min(cnt[0][2], cnt[2][0]);
cnt[0][2] -= t; cnt[2][0] -= t; ans += t;
t = min(cnt[1][2], cnt[2][1]);
cnt[1][2] -= t; cnt[2][1] -= t; ans += t;
int add=0;
for (int x=0; x<3; x++) for (int y=0; y<3; y++) if (x!=y) add += cnt[x][y];
(add /= 3) *= 2;
return ans += add;
}
