/**
__author__ : FireGhost
problems_ID: ioi21_dna
*/
#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
const int N = 1e5 + 3;
const int MOD = 1e9 + 7;
int pref_AT[N], pref_TA[N], pref_AC[N], pref_CA[N], pref_TC[N], pref_CT[N];
void init(string a, string b) {
int n = a.size();
a = " " + a; b = " " + b;
for (int i = 1; i <= n; ++i) {
pref_AT[i] = pref_AT[i - 1] + (a[i] == 'A' && b[i] == 'T');
pref_TA[i] = pref_TA[i - 1] + (a[i] == 'T' && b[i] == 'A');
pref_AC[i] = pref_AC[i - 1] + (a[i] == 'A' && b[i] == 'C');
pref_CA[i] = pref_CA[i - 1] + (a[i] == 'C' && b[i] == 'A');
pref_TC[i] = pref_TC[i - 1] + (a[i] == 'T' && b[i] == 'C');
pref_CT[i] = pref_CT[i - 1] + (a[i] == 'C' && b[i] == 'T');
}
}
int get_distance(int x, int y) {
++x, ++y;
int ans = 0;
int AT = pref_AT[y] - pref_AT[x - 1];
int TA = pref_TA[y] - pref_TA[x - 1];
int AC = pref_AC[y] - pref_AC[x - 1];
int CA = pref_CA[y] - pref_CA[x - 1];
int TC = pref_TC[y] - pref_TC[x - 1];
int CT = pref_CT[y] - pref_CT[x - 1];
int i = min(AT, TA), j = min(AC, CA), k = min(TC, CT);
ans += i + j + k;
AT -= i, TA -= i, AC -= j, CA -= j, TC -= k, CT -= k;
int A = AT + AC - TA - CA, C = CA + CT - AC - TC, T = TA + TC - AT - CT;
if (A > 0 || T > 0 || C > 0)
return -1;
if (AT == 0) {
if (TA != AC || AC != CT)
return -1;
ans += 2 * TA;
}
else {
if (AT != TC || TC != CA)
return -1;
ans += 2 * AT;
}
return ans;
}
