#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<char, char>;
string a, b;
vector<char> x = {'A', 'C', 'T'};
void init(string as, string bs){
a = as; b = bs;
}
int get_distance(int l, int r){
map<char, int> mp;
for (int i = l; i <= r; i++){
mp[a[i]]++;
mp[b[i]]--;
}
for (auto t: mp){
if (t.second != 0){
return -1;
}
}
map<pii, int> cnt;
for (int i = l; i <= r; i++){
if (a[i] == b[i]) continue;
cnt[{a[i], b[i]}]++;
}
vector<pii> arr;
for (auto [u, v]: cnt){
arr.push_back(u);
}
int out = 0;
for (auto p1: arr){
pii p2 = {p1.second, p1.first};
if (cnt.find(p2) == cnt.end()){
continue;
}
int k1 = cnt[p1], k2 = cnt[p2];
out += min(k1, k2);
if (k1 > k2){
cnt.erase(p2);
cnt[p1] -= k2;
}
else {
cnt.erase(p1);
cnt[p2] -= k1;
if (!cnt[p2]){
cnt.erase(p2);
}
}
}
vector<int> f;
for (auto [u, v]: cnt) f.push_back(v);
sort(f.begin(), f.end());
// f.back() -= f[0]
while (f.size() > 1){
out += f[0];
f.back() -= f[0];
f.erase(f.begin());
if (!f.back()) f.pop_back();
sort(f.begin(), f.end());
}
if (!f.empty()) out += f[0];
return out;
}
