#include "dna.h"
#include <bits/stdc++.h>
namespace ecnerwala {
std::vector<std::array<int, 9>> pref;
}
void init(std::string A, std::string B) {
using namespace ecnerwala;
assert(A.size() == B.size());
int N = int(A.size());
pref.resize(N+1);
pref[0].fill(0);
auto char_to_val = [](char c) -> int {
switch (c) {
case 'A': return 0;
case 'C': return 1;
case 'T': return 2;
default: assert(false);
}
};
for (int i = 0; i < N; i++) {
pref[i+1] = pref[i];
++pref[i+1][char_to_val(A[i]) * 3 + char_to_val(B[i])];
}
}
int get_distance(int x, int y) {
using namespace ecnerwala;
y++;
assert(0 <= x && x < y && y < int(pref.size()));
std::array<int, 9> cnt;
for (int i = 0; i < 9; i++) cnt[i] = pref[y][i] - pref[x][i];
int d1 = cnt[1] - cnt[3];
int d2 = cnt[5] - cnt[7];
int d3 = cnt[6] - cnt[2];
if (d1 != d2 || d2 != d3) return -1;
int ans = 0;
ans += std::min(cnt[1], cnt[3]);
ans += std::min(cnt[2], cnt[6]);
ans += std::min(cnt[7], cnt[5]);
ans += std::abs(d1) * 2;
return ans;
}
