#include "dna.h"
#include "bits/stdc++.h"
using namespace std;
int N;
char ch[]={'A','C','T'};
int prefA[100005][3],prefB[100005][3],pref[100005],prefp[100005][6];
void init(std::string a, std::string b) {
N=a.length();
for(int i=1;i<=N;i++){
for(int j=0;j<3;j++){
prefA[i][j]=prefA[i-1][j];
prefB[i][j]=prefB[i-1][j];
if(a[i-1]==ch[j]){
prefA[i][j]++;
}
if(b[i-1]==ch[j]){
prefB[i][j]++;
}
}
pref[i]=pref[i-1]+(a[i-1]!=b[i-1]);
prefp[i][0]=prefp[i-1][0];
if(a[i-1]==ch[0] && b[i-1]==ch[1])prefp[i][0]++;
prefp[i][1]=prefp[i-1][1];
if(a[i-1]==ch[1] && b[i-1]==ch[0])prefp[i][1]++;
prefp[i][2]=prefp[i-1][2];
if(a[i-1]==ch[0] && b[i-1]==ch[2])prefp[i][2]++;
prefp[i][3]=prefp[i-1][3];
if(a[i-1]==ch[2] && b[i-1]==ch[0])prefp[i][3]++;
prefp[i][4]=prefp[i-1][4];
if(a[i-1]==ch[1] && b[i-1]==ch[2])prefp[i][4]++;
prefp[i][5]=prefp[i-1][5];
if(a[i-1]==ch[2] && b[i-1]==ch[1])prefp[i][5]++;
}
}
int get_distance(int x, int y) {
x++;y++;
for(int i=0;i<3;i++){
if(prefA[y][i]-prefA[x-1][i]!=prefB[y][i]-prefB[x-1][i])return -1;
}
int beda=pref[y]-pref[x-1];
int ans=0;
beda-=2*min(prefp[y][0]-prefp[x-1][0],prefp[y][1]-prefp[x-1][1]);
ans+=min(prefp[y][0]-prefp[x-1][0],prefp[y][1]-prefp[x-1][1]);
beda-=2*min(prefp[y][2]-prefp[x-1][2],prefp[y][3]-prefp[x-1][3]);
ans+=min(prefp[y][2]-prefp[x-1][2],prefp[y][3]-prefp[x-1][3]);
beda-=2*min(prefp[y][4]-prefp[x-1][4],prefp[y][5]-prefp[x-1][5]);
ans+=min(prefp[y][4]-prefp[x-1][4],prefp[y][5]-prefp[x-1][5]);
ans+=(beda/3)*2;
return ans;
}
