#include "dna.h"
using namespace std;
const int N = 1e5 + 100;
int cnt[N][3][3];
void transform(string& s) {
for(char& ch : s) {
if(ch == 'A') ch = '0';
else if(ch == 'T') ch = '1';
else ch = '2';
}
}
void init(string a, string b) {
transform(a);
transform(b);
int n = a.size();
for(int i = 1; i <= n; ++i) {
for(int k = 0; k < 3; ++k)
for(int j = 0; j < 3; ++j)
cnt[i][k][j] = cnt[i - 1][k][j];
++cnt[i][a[i - 1] - '0'][b[i - 1] - '0'];
}
}
int get_distance(int x, int y) {
int f[3][3] = {{0}}, X[3] = {0}, Y[3] = {0}, pairs = 0, triples = 0;
++x, ++y;
for(int i = 0; i < 3; ++i) {
for(int j = 0; j < 3; ++j) {
f[i][j] += cnt[y][i][j] - cnt[x - 1][i][j];
X[i] += cnt[y][i][j] - cnt[x - 1][i][j];
Y[j] += cnt[y][i][j] - cnt[x - 1][i][j];
}
}
for(int i = 0; i < 3; ++i) {
if(X[i] != Y[i])
return -1;
}
for(int i = 0; i < 3; ++i) {
for(int j = i + 1; j < 3; ++j) {
int X = min(f[i][j], f[j][i]);
f[i][j] -= X;
f[j][i] -= X;
pairs += X;
}
}
for(int i = 0; i < 3; ++i) {
for(int j = 0; j < 3; ++j) {
if(i == j) continue;
triples += f[i][j];
}
}
return pairs + 2 * triples / 3;
}
