#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
#define MAXI (int)1e5
#define pb(x) push_back(x)
int s1A[(int)1e5+5];
int s1T[(int)1e5+5];
int s2A[(int)1e5+5];
int s2T[(int)1e5+5];
int falsch[(int)1e5+5];
char s1[(int)1e5+5];
char s2[(int)1e5+5];
void init(string x,string y){
s1A[0] = s1T[0] = 0;
s2A[0] = s2T[0] = falsch[0] = 0;
int n = x.length();
for(int i = 0;i<n;i++){
s1[i] = x[i];
s2[i] = y[i];
s1A[i+1] = s1A[i];
s2A[i+1] = s2A[i];
s1T[i+1] = s1T[i];
s2T[i+1] = s2T[i];
falsch[i+1] = falsch[i];
if(x[i] == 'A') s1A[i+1]++;
if(y[i] == 'A') s2A[i+1]++;
if(x[i] == 'T') s1T[i+1]++;
if(y[i] == 'T') s2T[i+1]++;
if(x[i] != y[i]) falsch[i+1]++;
}
}
int get_distance(int x,int y){
++x; ++y;
if(s1A[y]-s1A[x-1] != s2A[y]-s2A[x-1] || s1T[y]-s1T[x-1] != s2T[y]-s2T[x-1]) return -1;
map<pair<char,char>,int> m;
int ans = 0;
for(int i = x-1;i<y;i++){
if(s1[i] == s2[i]) continue;
if(m[{s2[i],s1[i]}] > 0){
m[{s2[i],s1[i]}]--;
}else{
if(m.find({s1[i],s2[i]}) != m.end())
m[{s1[i],s2[i]}]++;
else m.insert({{s1[i],s2[i]},1});
ans++;
}
}
return ans;
}
