#include <bits/stdc++.h>
#include "dna.h"
using namespace std;
const int maxn = 1e5 + 3;
int get_code(char ch) {
if (ch == 'A')
return 0;
if (ch == 'C')
return 1;
return 2;
}
int cnt[maxn][3][3], cnt1[maxn][3], cnt2[maxn][3];
void init(string a, string b) {
for (int i = 0; i < (int)a.size(); i++) {
for (int j = 0; j < 3; j++)
for (int k = 0; k < 3; k++)
cnt[i][j][k] = (i ? cnt[i-1][j][k] : 0);
cnt[i][get_code(a[i])][get_code(b[i])]++;
for (int j = 0; j < 3; j++) {
cnt1[i][j] = (i ? cnt1[i - 1][j] : 0);
cnt2[i][j] = (i ? cnt2[i - 1][j] : 0);
}
cnt1[i][get_code(a[i])]++;
cnt2[i][get_code(b[i])]++;
}
}
int temp[3][3];
int get_distance(int l, int r) {
for (int i = 0; i < 3; i++)
if (cnt1[r][i] - cnt1[l-1][i] != cnt2[r][i] - cnt2[l-1][i])
return -1;
for (int i = 0; i < 3; i++)
for (int j = 0; j < 3; j++)
temp[i][j] = cnt[r][i][j] - cnt[l-1][i][j];
int ans = 0, left = r - l + 1;
for (int i = 0; i < 3; i++)
for (int j = i + 1; j < 3; j++) {
int mins = min(temp[i][j], temp[j][i]);
temp[i][j] -= mins;
temp[j][i] -= mins;
ans += mins;
left -= mins * 2;
}
for (int i = 0; i < 3; i++)
left -= temp[i][i];
ans += left * 2 / 3;
return ans;
}
/*
int main() {
init("ATACAT", "ACTATA");
cout << get_distance(4, 5) << endl;
}
*/
