#include <bits/stdc++.h>
#include "dna.h"
using namespace std;
#define fi first
#define se second
const int mxN = 2e5+10;
map<char,int> mp;
int n,same[mxN],prefA[mxN][2],prefB[mxN][2];
string A,B;
void init(string a,string b){
A=a,B=b;
n=a.size();
same[0]=(a[0]==b[0]);
mp['A']=0,mp['T']=1;
for(int i=1;i<n;++i){
same[i]=same[i-1]+(a[i]==b[i]);
}
for(int i=0;i<n;++i){
prefA[i][mp[A[i]]]=1;
prefB[i][mp[B[i]]]=1;
if(i>0){
prefA[i][0]+=prefA[i-1][0];
prefA[i][1]+=prefA[i-1][1];
prefB[i][0]+=prefB[i-1][0];
prefB[i][1]+=prefB[i-1][1];
}
}
}
bool ok(int l,int r){
int prefaA=prefA[l-(l!=0)][0];
int prefaT=prefA[l-(l!=0)][1];
int act_aA=prefA[r][0]-prefaA;
int act_aT=prefA[r][1]-prefaT;
int prefbA=prefB[l-(l!=0)][0];
int prefbT=prefB[l-(l!=0)][1];
int act_bA=prefB[r][0]-prefbA;
int act_bT=prefB[r][1]-prefbT;
if(act_aA!=act_bA||act_aT!=act_bT) return 0;
return 1;
}
int qry(int l,int r){
if(l==0) return same[r];
return same[r]-same[l-1];
}
int get_distance(int l,int r){
if(qry(l,r)==(r-l+1)) return 0;
if(!ok(l,r)) return -1;
return (r-l+1-qry(l,r))/2;
}
