#include "dna.h"
#include<bits/stdc++.h>
using namespace std;
#define vec vector
#define arr array
const int MXN = 100'005;
arr<arr<int, 3>, 3> psum_pref[MXN+1];
void init(std::string a, std::string b) {
map<char, int> chtoid;
chtoid['A'] = 0;
chtoid['C'] = 1;
chtoid['T'] = 2;
int n = a.size();
//cerr << a << '\n';
for(int i = 1; i<=n; i++) {
psum_pref[i] = psum_pref[i-1];
psum_pref[i][chtoid[a[i-1]]][chtoid[b[i-1]]]++;
}
}
int get_distance(int x, int y) {
auto psum_range = psum_pref[y+1];
arr<int, 3> a_cnt{0, 0, 0};
arr<int, 3> b_cnt{0, 0, 0};
for(int i = 0; i<3; i++) {
for(int j = 0; j<3; j++) {
psum_range[i][j] -= psum_pref[x][i][j];
a_cnt[i] += psum_range[i][j];
b_cnt[j] += psum_range[i][j];
}
}
for(int i = 0; i<3; i++) {
if(a_cnt[i] != b_cnt[i]) return -1;
}
int ans = 0;
for(int i = 0; i<3; i++) {
for(int j = i+1; j<3; j++) {
int com = min(psum_range[i][j], psum_range[j][i]);
ans += com;
psum_range[i][j] -= com;
psum_range[j][i] -= com;
}
}
vec<int> rem(0);
for(int i = 0; i<3; i++) {
for(int j = 0; j<3; j++) {
if(i == j) continue;
if(psum_range[i][j] > 0) rem.push_back(psum_range[i][j]);
}
}
assert(rem.size() <= 3);
if(rem.size() == 0) return ans;
if(rem.size() < 3) return -1;
bool eq = rem[0] == rem[1] && rem[1] == rem[2];
if(!eq) return -1;
ans += rem[0]*2;
return ans;
}
