#include "dna.h"
#include<bits/stdc++.h>
using namespace std;
vector<int> ax, at, ta, ct;
void init(std::string a, std::string b) {
int n = (int)a.size();
ax.resize(n + 1);
at.resize(n + 1);
ta.resize(n + 1);
ct.resize(n + 1);
for(int i = 0; i < n; i++){
ax[i + 1] = ax[i];
at[i + 1] = at[i];
ta[i + 1] = ta[i];
ct[i + 1] = ct[i];
if(a[i] == 'A' && b[i] != 'A'){
ax[i + 1] += 1;
}
if(a[i] == 'A' && b[i] == 'T'){
at[i + 1] += 1;
}
if(a[i] == 'T' && b[i] == 'A'){
ta[i + 1] += 1;
}
if(a[i] == 'C' && b[i] == 'T'){
ct[i + 1] += 1;
}
if(a[i] == 'T' && b[i] == 'C'){
ct[i + 1] += 1;
}
}
}
int get_distance(int x, int y) {
x += 1;
y += 1;
int AX = ax[y] - ax[x - 1];
int AT = at[y] - at[x - 1];
int TA = ta[y] - ta[x - 1];
int CT = ct[y] - ct[x - 1];
if((CT + abs(AT - TA)) % 2 == 1){
return -1;
} else{
return AX + (CT + abs(AT - TA)) / 2;
}
}
