#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
const int N = 100'001;
int AT[N], TA[N], AC[N], CA[N], CT[N], TC[N];
void init(string a, string b) {
int n = (int)a.size();
for (int i=0;i<n;i++){
AT[i] = (i==0?0:AT[i-1]) + (a[i] == 'A' && b[i] == 'T');
TA[i] = (i==0?0:TA[i-1]) + (a[i] == 'T' && b[i] == 'A');
AC[i] = (i==0?0:AC[i-1]) + (a[i] == 'A' && b[i] == 'C');
CA[i] = (i==0?0:CA[i-1]) + (a[i] == 'C' && b[i] == 'A');
CT[i] = (i==0?0:CT[i-1]) + (a[i] == 'C' && b[i] == 'T');
TC[i] = (i==0?0:TC[i-1]) + (a[i] == 'T' && b[i] == 'C');
}
}
int get_distance(int x, int y) {
int at = AT[y] - (x==0?0:AT[x-1]);
int ta = TA[y] - (x==0?0:TA[x-1]);
int ac = AC[y] - (x==0?0:AC[x-1]);
int ca = CA[y] - (x==0?0:CA[x-1]);
int ct = CT[y] - (x==0?0:CT[x-1]);
int tc = TC[y] - (x==0?0:TC[x-1]);
int ans = 0;
int m1=min(at, ta), m2=min(ac,ca), m3=min(tc,ct);
at -= m1, ta -= m1;
ac -= m2, ca -= m2;
tc -= m3, ct -= m3;
ans += m1 + m2 + m3;
int fa = at-ta + ac - ca;
int ft = ta-at + tc - ct;
int fc = ca-ac + ct - tc;
if (fa != 0 || ft != 0 || fc != 0) {
return -1;
}
int sum = at + ta + ac + ca + ct + tc;
return ans + (sum/3)*2;
}
