#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];
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]);
}
}
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;
}
return (pref[y]-pref[x-1]+1)/2;
}
