#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
string s, s1;
vector<int> dif;
vector<array<int, 3>> need, got;
vector<map<string, int>> seq;
void init(string a, string b){
s = a;
s1 = b;
dif.assign(s.size(), 0);
need.assign(s.size(), {0,0,0});
got.assign(s.size(), {0,0,0});
map<char, int> _map = {{'A',0},{'C',1},{'T',2}};
map<string, int> map2 = {{"AT",0},{"TA", 0},{"AC",0},{"CA",0},{"CT",0},{"TC", 0}};
vector<int> n1(3,0), n2(3,0);
seq.resize(s.size());
int t = 0, diff = 0;
for(int i = 0; i < s.size(); i ++){
string lo = string(1, s1[i]), ol = string(1, s[i]);
string lol = lo + ol;
if(s1[i] != s[i]){
map2[lol]++;
n1[_map[s[i]]]++;
n2[_map[s1[i]]]++;
diff++;
}
for(auto[l,r]:map2){
seq[i][l] = r;
}
for(int j = 0; j < 3; j ++){
need[i][j] = n1[j];
got[i][j] = n2[j];
}
dif[i] = diff;
}
}
int get_distance(int x, int y){
int score = 0;
array<int, 3> d1, d2;
map<string, int> retard;
for(int i = 0; i < 3; i ++){
d1[i] = need[y][i] - (x > 0 ? need[x-1][i] : 0);
d2[i] = got[y][i] - (x > 0 ? got[x-1][i] : 0);
}
for(auto [l,r] : seq[y]){
int a = r - (x > 0 ? seq[x-1][l] : 0);
retard[l] = a;
}
int irl = 0;
for(auto [l, r] : retard){
int t = min(r, retard[string(1,l[1]) + string(1,l[0])]);
retard[l] -= t;
retard[string(1,l[1]) + string(1,l[0])] -= t;
score += t;
irl += retard[l];
}
if(d1 != d2){
return -1;
}
else{
return score + irl * 2 / 3;
}
}
