#include "dna.h"
#include <bits/stdc++.h>
#define ll long long int
using namespace std;
string a, b; int n;
vector<ll> as, bs;
// A = 0, T = 1
vector<int> t;
void upd(int v, int tl, int tr, int pos, int val) {
if (tl == tr) {t[v] = val; return;}
int tm = (tl + tr) / 2;
if (pos <= tm) upd(2*v, tl, tm, pos, val);
else upd(2*v+1, tm+1, tr, pos, val);
t[v] = t[2*v] + t[2*v+1];
}
ll query(int v, int tl, int tr, int l, int r) {
if (l > r) return 0;
if (l == tl && r == tr) return t[v];
int tm = (tl + tr) / 2;
ll lf = query(2*v, tl, tm, l, min(tm, r));
ll rg = query(2*v+1, tm+1, tr, max(tm+1, l), r);
return lf + rg;
}
int get_distance(int x, int y) {
if (x == y) {
if (a[x] == b[x]) return 0;
return -1;
}
if (x + 1 == y) {
if (a[x] == b[x] && a[y] == b[y]) return 0;
if (a[x] == b[y] && a[y] == b[x]) return 1;
return -1;
}
ll suma = as[y], sumb = bs[y];
if (x > 0) {
suma -= as[x-1]; sumb -= bs[x-1];
}
if (suma != sumb) return -1;
ll ans = query(1, 1, (1LL << 17), x+1, y+1);
return ans/2;
}
// int main() { // COMMENT THIS
// string aa, bb; cin >> aa >> bb; // COMMENT THIS
void init(string aa, string bb) {
a = aa; b = bb; n = a.size();
as.resize(n); bs.resize(n);
if (a[0] == 'T') as[0]++;
if (b[0] == 'T') bs[0]++;
for (int i = 1; i < n; i++) {
as[i] = as[i-1];
bs[i] = bs[i-1];
if (a[i] == 'T') as[i]++;
if (b[i] == 'T') bs[i]++;
}
t.assign((1LL << 18), 0LL);
for (int i = 0; i < n; i++) {
if (a[i] != b[i]) {
upd(1, 1, (1LL << 17), i+1, 1);
}
}
}
