#ifndef EVAL
#include "grader.cpp"
#endif
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,n) for (long long i = 0; i < (n); i++)
#define FORS(i,s,n) for (long long i = (s); i < (n); i++)
#define FORR(i,n) for (long long i = (n)-1; i >= 0; i--)
#define NL '\n'
#define EL cout << NL
#define PRINTV(v) for (auto a: v) {cout << a << " ";} EL;
#define PRINTVV(v) for (auto a: v) {PRINTV(a);}
#define f first
#define s second
#define all(v) (v).first(), (v).second()
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll,ll> pl;
typedef vector<pl> vpl;
typedef vector<vpl> vvpl;
vvpl psum;
void init(std::string a, std::string b) {
ll n = a.size();
psum.assign(n,vpl(3,{0,0}));
vpl cur(3,{0,0});
FOR(i,n) {
if (a[i] == 'A' && b[i] == 'T') cur[0].f++;
if (a[i] == 'T' && b[i] == 'A') cur[0].s++;
if (a[i] == 'T' && b[i] == 'C') cur[1].f++;
if (a[i] == 'C' && b[i] == 'T') cur[1].s++;
if (a[i] == 'C' && b[i] == 'A') cur[2].f++;
if (a[i] == 'A' && b[i] == 'C') cur[2].s++;
psum[i] = cur;
}
}
int get_distance(int x, int y) {
vpl cnt(3,{0,0});
FOR(k,3) {
cnt[k].f += psum[y][k].f;
cnt[k].s += psum[y][k].s;
if (x > 0) {
cnt[k].f -= psum[x-1][k].f;
cnt[k].s -= psum[x-1][k].s;
}
}
bool ok = true;
if (cnt[0].s+cnt[2].f != cnt[0].f+cnt[2].s) ok = false;
if (cnt[1].s+cnt[0].f != cnt[1].f+cnt[0].s) ok = false;
if (cnt[2].s+cnt[1].f != cnt[2].f+cnt[1].s) ok = false;
if (!ok) return -1;
ll ans = 0;
FOR(k,3) {
if (cnt[k].s > cnt[k].f) swap(cnt[k].s,cnt[k].f);
ans += cnt[k].s;
cnt[k].f -= cnt[k].s;
}
ans += 2*cnt[0].f;
return ans;
}
