#include"bits/stdc++.h"
using namespace std;
using ll=long long;
#define S second
#define F first
const char ch[]={'A','C','T'};
int id(char c){
if(c=='A')return 0;
if(c=='T')return 1;
return 2;
}
int nd[1000001][3][3],n;
string a,b;
void init(string A, string B){
n=A.size();
a='#'+A,b='#'+B;
for(int i=1;i<=n;i++){
nd[i][id('A')][id('T')]=nd[i-1][id('A')][id('T')];
nd[i][id('A')][id('C')]=nd[i-1][id('A')][id('C')];
nd[i][id('T')][id('A')]=nd[i-1][id('T')][id('A')];
nd[i][id('T')][id('C')]=nd[i-1][id('T')][id('C')];
nd[i][id('C')][id('A')]=nd[i-1][id('C')][id('A')];
nd[i][id('C')][id('T')]=nd[i-1][id('C')][id('T')];
nd[i][id('A')][id('A')]=nd[i-1][id('A')][id('A')];
nd[i][id('C')][id('C')]=nd[i-1][id('C')][id('C')];
nd[i][id('T')][id('T')]=nd[i-1][id('T')][id('T')];
nd[i][id(a[i])][id(b[i])]++;
}
}
int get_distance(int l, int r){
l++; r++; // convert 0-based query to 1-based prefix
int f[3][3]={},frq[3]={};
for(char i:ch){
for(char j:ch){
f[id(i)][id(j)]=nd[r][id(i)][id(j)]-nd[l-1][id(i)][id(j)];
frq[id(i)]+=f[id(i)][id(j)];
frq[id(j)]-=f[id(i)][id(j)];
}
}
for(char i:ch)if(frq[id(i)])return -1;
int res=0;
for(char i:ch){
for(char j:ch){
if(j<=i)continue;
int m=min(f[id(i)][id(j)],f[id(j)][id(i)]);
f[id(i)][id(j)]-=m;
f[id(j)][id(i)]-=m;
res+=m;
}
}
int s=0;
for(char i:ch)for(char j:ch)if(i!=j)s+=f[id(i)][id(j)];
return res+2*(s/3);
}
// MalekLoky 3mk
