#include "dna.h"
#include<bits/stdc++.h>
#define in insert
#define pb push_back
using namespace std;
const int N=1e5+5;
int n,B[N],C[N],pref[2][N][4],d[N][2];
void init(std::string a, std::string b){
n=a.size();
for(int i=1;i<=n;i++){
if(a[i-1]=='A') B[i]=1;
else if(a[i-1]=='T') B[i]=2;
else B[i]=3;
}
for(int i=1;i<=n;i++){
if(b[i-1]=='A') C[i]=1;
else if(b[i-1]=='T') C[i]=2;
else C[i]=3;
}
for(int i=1;i<=n;i++){
for(int j=1;j<=3;j++){
pref[0][i][j]=pref[0][i-1][j]+bool(B[i]==j);
pref[1][i][j]=pref[1][i-1][j]+bool(C[i]==j);
}
}
return ;
}
int get_distance(int x, int y){
++x;++y;
bool can=1;
for(int j=1;j<=3;j++){
if(pref[0][y][j]-pref[0][x-1][j]!=pref[1][y][j]-pref[1][x-1][j]) can=0;
}
if(!can) return -1;
int ret=0;
int cnt[4][4];
memset(cnt,0,sizeof cnt);
for(int i=x;i<=y;i++){
if(B[i]==C[i]) continue ;
cnt[B[i]][C[i]]++;
}
for(int i=1;i<=3;i++){
for(int j=i+1;j<=3;j++){
int most=min(cnt[i][j],cnt[j][i]);
cnt[i][j]-=most;
cnt[j][i]-=most;
ret+=most;
}
}
//cout<<" # "<<ret<<' '<<endl;
int sum=0;
for(int i=1;i<=3;i++){
for(int j=1;j<=3;j++){
if(i==j) continue ;
sum+=cnt[i][j];
}
}
ret+=(sum/3)*2;
return ret;
}
