#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
int n, S[100005][3], P[100005][7], s[3], p[6];
int ch(char c)
{
if (c == 'A')
return 0;
if (c == 'T')
return 1;
return 2;
}
int pch(char c, char d)
{
if (c == 'A' && d == 'T')
return 0;
if (c == 'T' && d == 'A')
return 1;
if (c == 'A' && d == 'C')
return 2;
if (c == 'C' && d == 'A')
return 3;
if (c == 'C' && d == 'T')
return 4;
if (c == 'T' && d == 'C')
return 5;
return 6;
}
void init(std::string a, std::string b)
{
n = a.size();
a = ' ' + a;
b = ' ' + b;
for (int i = 1; i <= n; i++)
S[i][ch(a[i])]++, S[i][ch(b[i])]--, P[i][pch(a[i], b[i])]++;
for (int i = 1; i <= n; i++)
{
for (int j = 0; j < 3; j++)
S[i][j] += S[i - 1][j];
for (int j = 0; j < 6; j++)
P[i][j] += P[i - 1][j];
}
}
int get_distance(int x, int y)
{
y++;
for (int j = 0; j < 3; j++)
{
s[j] = S[y][j] - S[x][j];
if (s[j])
return -1;
}
for (int j = 0; j < 6; j++)
p[j] = P[y][j] - P[x][j];
int ans = 0;
for (int j = 0; j < 6; j += 2)
{
int m = min(p[j], p[j ^ 1]);
ans += m;
p[j] -= m;
p[j ^ 1] -= m;
}
return ans + max(p[0], p[1]) * 2;
}
