#include "dna.h"
#include "bits/stdc++.h"
using namespace std;
const int N = 1e5 + 6;
int pa[N][3], pb[N][3], p[N];
string a_, b_;
map < char , int > ch;
void init(string a, string b){
int n = (int)a.size();
a = '#' + a;
b = '#' + b;
a_ = a, b_ = b;
ch['A'] = 0, ch['C'] = 1, ch['T'] = 2;
for(int i = 1; i <= n; i++){
pa[i][ch[a[i]]]++;
pb[i][ch[b[i]]]++;
for(int c = 0; c < 3; c++){
pa[i][c] += pa[i - 1][c];
pb[i][c] += pb[i - 1][c];
}
}
for(int i = 1; i <= n; i++)
p[i] = p[i - 1] + (a[i] != b[i]);
}
int get_distance(int x, int y){
x++, y++;
for(int i = 0; i < 3; i++){
if(pb[y][i] - pb[x - 1][i] != pa[y][i] - pa[x - 1][i])
return -1;
}
return (p[y] - p[x - 1]) / 2;
}
