#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
string x,y;
int n;
vector<int> psum,cantiAa,cantiAb;
void init(string a,string b){
x=a;y=b;
n=a.size();
psum.resize(n+1);
cantiAa.resize(n+1);
cantiAb.resize(n+1);
for(int i=1;i<=n;i++){
cantiAa[i]=cantiAa[i-1]+(a[i-1]=='A');
cantiAb[i]=cantiAb[i-1]+(b[i-1]=='A');
psum[i]=psum[i-1]+(a[i-1]!=b[i-1]);
}
}
int get_distance(int x, int y){
if(cantiAa[y+1]-cantiAa[x]==cantiAb[y+1]-cantiAb[x]){
return (psum[y+1]-psum[x])>>1;
}else{
return -1;
}
}
