#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define f0r(i, n) for (auto i = 0; i < (n); ++i)
#define fnr(i, n, k) for (auto i = (n); i < (k); ++i)
#define all(v) (v).begin(), (v).end()
#define pb push_back
#define F first
#define S second
#define ctn(x) cout << x << '\n'
#define forl(a, l) for (auto a : l)
#define ctl(l) for (auto &a : (l)) cout << a << ' '; cout << endl;
#define lb(v, x) (lower_bound(all(v), x) - begin(v))
#define ub(v, x) (upper_bound(all(v), x) - begin(v))
#define pq priority_queue
template <class T>
using V = vector<T>;
using ll = long long;
using vi = V<int>;
using vl = V<ll>;
using pi = pair<int, int>;
using ti = tuple<int, int, int>;
using Adj = V<vi>;
using vvi = V<vi>;
#include "dna.h"
vi pfA, pfT;
void init(string a, string b) {
int n = a.size();
pfA = pfT = vi(n+1);
f0r(i, n) {
pfA[i+1] = pfA[i], pfT[i+1] = pfT[i];
if (a[i] == b[i]) continue;
if (a[i] == 'T') pfT[i+1]++;
else pfA[i+1]++;
}
}
int get_distance(int x, int y) {
int A = pfA[y+1] - pfA[x], T = pfT[y+1] - pfT[x];
return A == T ? A : -1;
}
