#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
int p[6][1<<17], r[6];
void init(std::string s, std::string t) {
int n = s.size();
for (int i=0;i<n;++i)
{
for (int j=0;j<6;++j)
p[j][i+1] = p[j][i];
if (s[i] == 'A')
{
if (t[i] == 'T')
++p[0][i+1];
if (t[i] == 'C')
++p[1][i+1];
}
if (s[i] == 'T')
{
if (t[i] == 'A')
++p[2][i+1];
if (t[i] == 'C')
++p[3][i+1];
}
if (s[i] == 'C')
{
if (t[i] == 'A')
++p[4][i+1];
if (t[i] == 'T')
++p[5][i+1];
}
}
}
int pair_up(int x, int y)
{
int z = min(r[x], r[y]);
r[x] -= z;
r[y] -= z;
return z;
}
int get_distance(int x, int y)
{
int ans = 0;
++x;
++y;
for (int i=0;i<6;++i)
r[i] = p[i][y] - p[i][x-1];
if (r[0] + r[1] != r[2] + r[4] || r[2] + r[3] != r[0] + r[5] || r[4] + r[5] != r[1] + r[3])
return -1;
ans += pair_up(0, 2);
ans += pair_up(1, 4);
ans += pair_up(3, 5);
return ans + ((r[0] + r[1] + r[2] + r[3] + r[4] + r[5])/3)*2;
}
