#include "dna.h"
// author : sentheta aka vanwij
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<cassert>
#include<random>
#include<chrono>
#include<cmath>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<stack>
#include<map>
#include<set>
using namespace std;
#define Int long long
#define V vector
#define pb push_back
#define pii pair<int,int>
#define ff first
#define ss second
#define rand() (uniform_int_distribution<int>(0,1<<30)(rng))
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
#define pow2(x) (1LL<<(x))
#define msb(x) (63-__builtin_clzll(x))
#define bitcnt(x) (__builtin_popcountll(x))
#define nl '\n'
#define _ << ' ' <<
#define dbg(x) cout<<"?"<< #x <<" : "<<(x)<<endl; cout.flush();
#define rep(i,a,b) for(int i = (int)(a); i < (int)(b); i++)
#define all(x) (x).begin(), (x).end()
const int N = 1e5+5;
int n;
int cnt[3][N];
int p[3][3][N];
int f(char c){
if(c=='A') return 0;
if(c=='C') return 1;
if(c=='T') return 2;
return -1;
}
int qry(int l,int r,int* arr){
int ret = arr[r];
if(l) ret -= arr[l-1];
return ret;
}
void init(string s,string t){
n = s.size();
rep(i,0,n){
int x = f(s[i]), y = f(t[i]);
if(i){
rep(j,0,3) cnt[j][i] = cnt[j][i-1];
rep(j,0,3) rep(k,0,3)
p[j][k][i] = p[j][k][i-1];
}
else{
rep(j,0,3) cnt[j][i] = 0;
rep(j,0,3) rep(k,0,3)
p[j][k][i] = 0;
}
cnt[x][i]++;
cnt[y][i]--;
p[x][y][i]++;
}
}
int get_distance(int x,int y){
rep(i,0,3) if(qry(x,y,cnt[i]) != 0){
return -1;
}
int ans = 0;
int a[3][3];
rep(i,0,3) rep(j,0,3){
if(i!=j) a[i][j] = qry(x,y,p[i][j]);
else a[i][j] = 0;
}
// ij <--> ji
rep(i,0,3) rep(j,0,i){
int mov = min(a[i][j], a[j][i]);
ans += mov;
a[i][j] -= mov;
a[j][i] -= mov;
}
int rem = 0;
rep(i,0,3) rep(j,0,3){
rem += a[i][j];
}
ans += rem/3*2;
return ans;
}
