#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 10;
int n, prefa[maxn][3], prefb[maxn][3];
int is_cool[maxn], cool[maxn];
void init(std::string a, std::string b)
{
n = a.size();
for (int i = 0; i < a.size(); ++ i)
{
for (int j = 0; j < 3 && i; ++ j)
prefa[i][j] = prefa[i-1][j];
if(a[i] == 'A')prefa[i][0] ++;
else if(a[i] == 'T')prefa[i][1] ++;
else prefa[i][2] ++;
}
for (int i = 0; i < b.size(); ++ i)
{
for (int j = 0; j < 3 && i; ++ j)
prefb[i][j] = prefb[i-1][j];
if(b[i] == 'A')prefb[i][0] ++;
else if(b[i] == 'T')prefb[i][1] ++;
else prefb[i][2] ++;
}
for (int i = 0; i < n; ++ i)
{
if(i)cool[i] = cool[i-1];
if(a[i] == b[i])is_cool[i] = 1;
cool[i] += is_cool[i];
}
}
int geta(int lt, int rt, int t)
{
int cnt = prefa[rt][t];
if(lt > 0)cnt -= prefa[lt-1][t];
return cnt;
}
int getb(int lt, int rt, int t)
{
int cnt = prefb[rt][t];
if(lt > 0)cnt -= prefb[lt-1][t];
return cnt;
}
int get_distance(int x, int y)
{
for (int j = 0; j < 3; ++ j)
{
if(geta(x, y, j) != getb(x, y, j))return -1;
}
int ok = cool[y];
if(x)ok -= cool[x-1];
return max(0, (y - x + 1)/2);
}
