#include "dna.h"
#include<bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define all(x) x.begin(), x.end()
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
template<typename T>
using matrix= vector<vector<T>>;
array<vector<array<int,3>>,2> ct;
vector<array<array<int,3>,3>> fix;
map<char,int> dic = {{'A',0},{'C',1},{'T',2}};
void init(std::string a, std::string b) {
int n = a.size();
for(int i = 0; i < 2; i++){
ct[i] = vector<array<int,3>>(n+1);
}
fix = vector<array<array<int,3>,3>>(n+1);
for(int i = 1; i <= n; i++){
ct[0][i] = ct[0][i-1];
ct[0][i][dic[a[i-1]]]++;
}
for(int i = 1; i <= n; i++){
ct[1][i] = ct[1][i-1];
ct[1][i][dic[b[i-1]]]++;
fix[i] = fix[i-1];
fix[i][dic[a[i-1]]][dic[b[i-1]]]++;
}
}
int get_distance(int x, int y) {
array<int,3> c1 = ct[0][y+1], c2 = ct[1][y+1];
for(int i = 0; i < 3; i++)
c1[i]-=ct[0][x][i], c2[i] -=ct[1][x][i];
if(c1!=c2)
return -1;
int resp = 0;
array<array<int,3>,3> totfix = fix[y+1];
for(int i = 0; i < 3; i++){
for(int j = 0; j < 3; j++){
totfix[i][j]-=fix[x][i][j];
}
}
int tricicle = 0;
for(int i = 0; i < 3; i++){
for(int j = i+1; j < 3; j++){
int can = min(totfix[i][j],totfix[j][i]);
resp+=can;
totfix[i][j]-=can;
totfix[j][i]-=can;
tricicle+=totfix[i][j]+totfix[j][i];
}
}
resp+=tricicle/3*2;
return resp;
}
