#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
string as, bs;
vector<int> cc[3];
vector<int> lc[6];
char letters[3] = {'A', 'T', 'C'};
char combos[][3] = {{'A', 'T'}, {'A', 'C'}, {'T', 'C'}};
void init(string a, string b) {
as = a;
bs = b;
int n = a.length();
for (int i = 0; i < 3; ++i) {
cc[i].resize(n + 2, 0);
}
for (int i = 0; i < 6; ++i) {
lc[i].resize(n + 2, 0);
}
for (int i = 1; i <= n; ++i) {
for (int ci = 0; ci < 3; ++ci) {
cc[ci][i] = cc[ci][i - 1] +
((as[i - 1] == combos[ci][0] && bs[i - 1] == combos[ci][1]) ||
(as[i - 1] == combos[ci][1] && bs[i - 1] == combos[ci][0]));
lc[ci][i] = lc[ci][i - 1] + (as[i - 1] == letters[ci]);
lc[ci + 3][i] = lc[ci + 3][i - 1] + (bs[i - 1] == letters[ci]);
}
}
}
int get_distance(int x, int y) {
y++;
int c1 = cc[0][y] - cc[0][x];
int c2 = cc[1][y] - cc[1][x];
int c3 = cc[2][y] - cc[2][x];
int lc1 = lc[0][y] - lc[0][x];
int lc2 = lc[1][y] - lc[1][x];
int lc3 = lc[2][y] - lc[2][x];
int lc4 = lc[3][y] - lc[3][x];
int lc5 = lc[4][y] - lc[4][x];
int lc6 = lc[5][y] - lc[5][x];
int count = 0;
if (lc1 != lc4 || lc2 != lc5 || lc3 != lc6)
return -1;
int remaining = c1 + c2 + c3;
if (!(c1 & 1)) {
remaining -= c1;
count += c1 / 2;
}
if (!(c2 & 1)) {
remaining -= c2;
count += c2 / 2;
}
if (!(c3 & 1)) {
remaining -= c3;
count += c3 / 2;
}
if (remaining)
count += remaining / 3 * 2;
return count;
}
