#include "dna.h"
#include <bits/stdc++.h>
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
const int N = 1e5 + 50;
int ps[N][3][3], n;
inline short T(char c) {
switch(c) {
case 'A':
return 0;
case 'T':
return 1;
default:
return 2;
}
return -1;
}
void init(string a, string b) {
n = a.size();
ps[0][T(a[0])][T(b[0])] = 1;
FOR(i, 1, n) {
FOR(j, 0, 3) FOR(k, 0, 3) ps[i][j][k] = ps[i - 1][j][k];
ps[i][T(a[i])][T(b[i])]++;
}
}
int get_distance(int x, int y) {
int dp[3][3] = {0};
FOR(i, 0, 3) FOR(j, 0, 3) dp[i][j] = ps[y][i][j] - (x ? ps[x - 1][i][j] : 0);
int ans = 0;
FOR(i, 0, 3) FOR(j, i + 1, 3) {
int m = min(dp[i][j], dp[j][i]);
ans += m;
dp[i][j] -= m;
dp[j][i] -= m;
}
{
int m = min({dp[0][1], dp[1][2], dp[2][0]});
ans += 2 * m;
dp[0][1] -= m, dp[1][2] -= m, dp[2][0] -= m;
}
{
int m = min({dp[0][2], dp[2][1], dp[1][0]});
ans += 2 * m;
dp[0][2] -= m, dp[2][1] -= m, dp[1][0] -= m;
}
FOR(i, 0, 3) FOR(j, 0, 3) if (dp[i][j]) return -1;
return ans;
}
