#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<ll>;
using pl = pair<ll,ll>;
#define pb push_back
#define form(m,it) for(auto it=m.begin(); it!=m.end(); it++)
#define forp(i,a,b) for(ll i=a; i<=b; i++)
#define forn(i,a,b) for(ll i=a; i>=b; i--)
#define newl '\n'
ll cnt[3][3][100005];
ll seq[2][3][100005];
void init(string a, string b){
ll n=a.length();
forp(i,0,n-1){
a[i]=(a[i]=='T')?'B':a[i];
b[i]=(b[i]=='T')?'B':b[i];
}
forp(i,1,n){
forp(i1,0,2){
forp(i2,0,2){
if(a[i-1]==(char)(i1+'A')&&b[i-1]==(char)(i2+'A')){
cnt[i1][i2][i]=cnt[i1][i2][i-1]+1;
} else {
cnt[i1][i2][i]=cnt[i1][i2][i-1];
}
//cout<<(char)(i1+'A')<<" "<<(char)(i2+'A')<<" "<<i<<" "<<cnt[i1][i2][i]<<newl;
}
}
forp(j,0,2){
if(a[i-1]==(char)(j+'A')){
seq[0][j][i]=seq[0][j][i-1]+1;
} else {
seq[0][j][i]=seq[0][j][i-1];
}
if(b[i-1]==(char)(j+'A')){
seq[1][j][i]=seq[1][j][i-1]+1;
} else {
seq[1][j][i]=seq[1][j][i-1];
}
}
}
}
int get_distance(int x, int y){
x++; y++;
forp(j,0,2){
if(seq[0][j][y]-seq[0][j][x-1]!=seq[1][j][y]-seq[1][j][x-1]){
return -1;
}
}
ll c=0;
ll ans=0;
forp(i,0,2){
forp(j,i+1,2){
ans+=min((cnt[j][i][y]-cnt[j][i][x-1]),(cnt[i][j][y]-cnt[i][j][x-1]));
c+=2*min((cnt[j][i][y]-cnt[j][i][x-1]),(cnt[i][j][y]-cnt[i][j][x-1]));
}
c+=(cnt[i][i][y]-cnt[i][i][x-1]);
}
ans+=2*((y-x+1-c)/3);
return ans;
}
