#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
string a,b;
vector<int> prefa;
vector<int> prefb;
vector<int> prefa2;
vector<int> prefb2;
vector<int> prefdiff;
void init(std::string f, std::string s) {
a=f;b=s;
int n=a.size();
prefa.resize(n+2);
prefb.resize(n+2);
prefa2.resize(n+2);
prefb2.resize(n+2);
prefdiff.resize(n+2);
prefa[0]=0;
prefb[0]=0;
prefa2[0]=0;
prefb2[0]=0;
prefdiff[0]=0;
for(int i=1;i<=n+1;i++){
prefa[i]=prefa[i-1];
prefb[i]=prefb[i-1];
prefa2[i]=prefa2[i-1];
prefb2[i]=prefb2[i-1];
prefdiff[i]=prefdiff[i-1];
if(a[i-1]=='B')prefb[i]++;
if(a[i-1]=='A')prefa[i]++;
if(b[i-1]=='B')prefb2[i]++;
if(b[i-1]=='A')prefa2[i]++;
if(a[i-1]!=b[i-1])prefdiff[i]++;
}
}
int get_distance(int x, int y) {
if(prefa[y+1]-prefa[x]!=prefa2[y+1]-prefa2[x] || prefb[y+1]-prefb[x]!=prefb2[y+1]-prefb2[x])return -1;
int c=prefdiff[y+1]-prefdiff[x];
return c/2;
}
