#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
int enc[256];
int N, A[MAXN], B[MAXN];
int cnt[MAXN], cc[3][MAXN], pref[2][MAXN];
void init(std::string a, std::string b) {
enc['A'] = 0;
enc['C'] = 1;
enc['T'] = 2;
int N = a.size();
for(int i = 0; i < N; i++) {
A[i + 1] = enc[a[i]];
B[i + 1] = enc[b[i]];
}
for(int i = 1; i <= N; i++) {
for(int j = 0; j < 3; j++) {
cc[j][i] = cc[j][i - 1];
}
cnt[i] = cnt[i - 1];
pref[0][i] = pref[0][i - 1];
pref[1][i] = pref[1][i - 1];
cc[A[i]][i]++;
cc[B[i]][i]--;
if(A[i] != B[i]) {
cnt[i]++;
if(A[i] == 0 && B[i] == 1) {
pref[0][i]++;
}
if(A[i] == 1 && B[i] == 0) {
pref[1][i]++;
}
}
}
}
int get_distance(int x, int y) {
x++, y++;
for(int j = 0; j < 3; j++) {
if(cc[j][y] - cc[j][x - 1] != 0) {
return -1;
}
}
int D = (pref[0][y] - pref[0][x - 1]) - (pref[1][y] - pref[1][x - 1]);
if(D < 0) D = -D;
int Ans = (cnt[y] - cnt[x - 1] - 3*D) / 2 + 2*D;
return Ans;
}
