#include "dna.h"
#include "bits/stdc++.h"
using namespace std;
using un = int;
using vuc = vector<un>;
using vol = vector<bool>;
#define REP(i, a, b) for (un i = (un)a; i < (un)b; i++)
#define FEAC(i, a) for (auto&& i : a)
#define vec vector
#define ALL(x) (x).begin(), (x).end()
constexpr char A = 'A';
constexpr char B = 'T';
constexpr char C = 'C';
constexpr un AB = 0;
constexpr un BA = 1;
constexpr un BC = 2;
constexpr un CB = 3;
constexpr un AC = 4;
constexpr un CA = 5;
vec<vuc> prefixes;
un N;
void init(std::string X, std::string Y) {
N = X.size();
vec<vuc> events(6, vuc(N, 0));
REP(i, 0, N){
if ((X[i] == A) and (Y[i] == B)){
events[AB][i] = 1;
}
if ((X[i] == B) and (Y[i] == A)){
events[BA][i] = 1;
}
if ((X[i] == A) and (Y[i] == C)){
events[AC][i] = 1;
}
if ((X[i] == C) and (Y[i] == A)){
events[CA][i] = 1;
}
if ((X[i] == B) and (Y[i] == C)){
events[BC][i] = 1;
}
if ((X[i] == C) and (Y[i] == B)){
events[CB][i] = 1;
}
}
prefixes = vec<vuc>(6, vuc(N+1, 0));
REP(s, 0, 6) {
REP(i, 1, N+1){
prefixes[s][i] = prefixes[s][i-1] + events[s][i-1];
}
}
}
int get_distance(int x, int y) {
vuc rets(6, 0);
REP(s, 0, 6){
rets[s] = prefixes[s][y+1] - prefixes[s][x];
}
if ((rets[AB] + rets[AC]) != (rets[BA] + rets[CA])) return -1;
if ((rets[BA] + rets[BC]) != (rets[AB] + rets[CB])) return -1;
if ((rets[CA] + rets[CB]) != (rets[AC] + rets[BC])) return -1;
un ret = 0;
un m;
m = min(rets[AB], rets[BA]);
ret += m;
rets[AB] -= m;
rets[BA] -= m;
m = min(rets[BC], rets[CB]);
ret += m;
rets[BC] -= m;
rets[CB] -= m;
m = min(rets[AC], rets[CA]);
ret += m;
rets[AC] -= m;
rets[CA] -= m;
ret += 2*max(rets[AB], rets[BA]);
return ret;
}
