//IOI 2021
#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int cnta[N][3];
int cntb[N][3];
int ps[N][3][3];
void init(string a, string b){
int n=a.size();
vector<int> enc = {'A', 'C', 'T'};
map<char, int> dec;
dec['A']=0;
dec['C']=1;
dec['T']=2;
for(int i=0; i<n; i++){
for(int j=0; j<3; j++){
cnta[i+1][j] = cnta[i][j];
cntb[i+1][j] = cntb[i][j];
if(a[i] == enc[j]){
cnta[i+1][j]++;
}
if(b[i] == enc[j]){
cntb[i+1][j]++;
}
}
}
for(int i=0; i<n; i++){
for(int j=0; j<3; j++){
for(int k=0; k<3; k++){
ps[i+1][i][j] = ps[i][j][j];
}
}
int j = dec[a[i]];
int k = dec[b[i]];
if(j==k) continue;
ps[i+1][j][k]++;
}
}
int get_distance(int x, int y){
for(int j=0; j<3; j++){
if(cnta[y+1][j]-cnta[x][j] != cntb[y+1][j]-cntb[x][j]){
return -1;
}
}
int ans1=0;
int ans2=0;
for(int j=0; j<3; j++){
for(int k=0; k<j; k++){
int a=ps[y+1][j][k] - ps[x][j][k];
int b=ps[y+1][k][j] - ps[x][k][j];
ans1 += min(a, b);
ans2 += max(a, b)-min(a, b);
}
}
assert(ans2%3 == 0);
int ans = ans1 + 2*ans2/3;
return ans;
}
