#include <bits/stdc++.h>
using namespace std;
const int N = 2e5+5;
int n;
int prefaa[N],prefat[N],prefac[N],prefba[N],prefbt[N],prefbc[N];
int prefAT[N],prefTA[N],prefAC[N],prefCA[N],prefTC[N],prefCT[N];
void init(string a, string b) {
n = a.size();
a = " " + a;
b = " " + b;
for (int i = 1; i <= n; i++) {
prefaa[i] = prefaa[i-1] + (a[i] == 'A');
prefat[i] = prefat[i-1] + (a[i] == 'T');
prefac[i] = prefac[i-1] + (a[i] == 'C');
prefba[i] = prefba[i-1] + (b[i] == 'A');
prefbt[i] = prefbt[i-1] + (b[i] == 'T');
prefbc[i] = prefbc[i-1] + (b[i] == 'C');
}
for (int i = 1; i <= n ; i++) {
prefAT[i] = prefAT[i-1] + (a[i] == 'A' && b[i] == 'T');
prefTA[i] = prefTA[i-1] + (a[i] == 'T' && b[i] == 'A');
prefAC[i] = prefAC[i-1] + (a[i] == 'A' && b[i] == 'C');
prefCA[i] = prefCA[i-1] + (a[i] == 'C' && b[i] == 'A');
prefCT[i] = prefCT[i-1] + (a[i] == 'C' && b[i] == 'T');
prefTC[i] = prefTC[i-1] + (a[i] == 'T' && b[i] == 'C');
}
}
int get_distance(int x, int y) {
y++;
if (prefaa[y]-prefaa[x] != prefba[y]-prefba[x]) return -1;
if (prefat[y]-prefat[x] != prefbt[y]-prefbt[x]) return -1;
if (prefac[y]-prefac[x] != prefbc[y]-prefbc[x]) return -1;
int at = prefAT[y]-prefAT[x];
int ta = prefTA[y]-prefTA[x];
int ac = prefAC[y]-prefAC[x];
int ca = prefCA[y]-prefCA[x];
int ct = prefCT[y]-prefCT[x];
int tc = prefTC[y]-prefTC[x];
int mn1 = min(at,ta);
int mn2 = min(ac,ca);
int mn3 = min(ct,tc);
int ans = 0;
ans += (mn1 + mn2 + mn3);
at -= mn1; ta -= mn1;
ac -= mn2; ca -= mn2;
ct -= mn3; tc -= mn3;
ans += 2*max(at,ta);
return ans;
}
