#include <bits/stdc++.h>
using namespace std;
int n;
vector<int> aa, ba, diff;
vector<int> posA_a, posT_a, posC_a;
vector<int> posA_b, posT_b, posC_b;
void init(string a, string b) {
n=a.size();
aa.resize(n+1,0);
ba.resize(n+1,0);
diff.resize(n+1,0);
for (int i=0;i<n;i++) {
aa[i+1]=aa[i]+(a[i]=='A');
ba[i+1]=ba[i]+(b[i]=='A');
diff[i+1]=diff[i]+(a[i]!=ba[i]);
}
}
int get_distance(int x,int y) {
int len=y+1-x;
int cnta=aa[y+1]-aa[x];
int cntb=ba[y+1]-ba[x];
if (cnta!=cntb) return -1;
int re=diff[y+1]-diff[x];
return re/2;
}
