#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
int n,S[100005][3][3];
int getId(char c) {
if(c=='A')
return 0;
if(c=='C')
return 1;
return 2;
}
void init(std::string a, std::string b) {
n=a.size();
for(int i=0;i<n;i++) {
if(i>0)
for(int t1=0;t1<3;t1++)
for(int t2=0;t2<3;t2++)
S[i][t1][t2]=S[i-1][t1][t2];
S[i][getId(a[i])][getId(b[i])]++;
}
}
int get_distance(int x, int y) {
int C[3][3];
for(int t1=0;t1<3;t1++)
for(int t2=0;t2<3;t2++)
C[t1][t2]=S[y][t1][t2]-(x==0?0:S[x-1][t1][t2]);
if(C[0][1]+C[0][2]!=C[1][0]+C[2][0]||C[1][0]+C[1][2]!=C[0][1]+C[2][1])
return -1;
int s1=0,s2=1e9;
for(int t1=0;t1<3;t1++)
for(int t2=t1+1;t2<3;t2++) {
int tmp=min(C[t1][t2],C[t2][t1]);
C[t1][t2]-=tmp;
C[t2][t1]-=tmp;
s1+=tmp;
}
for(int t1=0;t1<3;t1++)
for(int t2=t1+1;t2<3;t2++)
s2=min(s2,max(C[t1][t2],C[t2][t1]));
return s1+2*s2;
}
