#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
#include "dna.h"
map<char, int> charToInt;
vector<vector<vi>> prefCnt;
int n;
void init(std::string a, std::string b) {
charToInt['A'] = 0;
charToInt['C'] = 1;
charToInt['T'] = 2;
n = sz(a);
prefCnt.resize(3, vector<vi>(3, vi(n+1)));
rep(i,0,n) {
rep(x,0,3) rep(y,0,3) prefCnt[x][y][i+1] = prefCnt[x][y][i];
prefCnt[charToInt[a[i]]][charToInt[b[i]]][i+1]++;
}
}
vi operator+(vi a, vi b) {
vi retvalue(3);
rep(i,0,3) retvalue[i] = a[i] + b[i];
return retvalue;
}
void print(vi a) {
trav(elem, a) cerr << elem << ", ";
cerr << endl;
}
int get_distance(int x, int y) {
vector<vi> swapsNeeded(3, vi(3));
rep(a,0,3) rep(b,0,3) {
swapsNeeded[a][b] = prefCnt[a][b][y+1] - prefCnt[a][b][x];
}
rep(i,0,3) {
int in = 0;
int out = 0;
rep(j,0,3) {
in += swapsNeeded[j][i];
out += swapsNeeded[i][j];
}
if (in != out) return -1;
}
int ans = 0;
rep(a,0,3) rep(b,a+1,3) {
int temp = min(swapsNeeded[a][b], swapsNeeded[b][a]);
ans += temp;
swapsNeeded[a][b] -= temp;
swapsNeeded[b][a] -= temp;
}
vector<pii> order({pii(0, 1), pii(0, 2), pii(1, 2)});
//cerr << "ans = " << ans << endl;
//cerr << "swapsNeeded = " << endl;
//trav(v, swapsNeeded)
// print(v);
//cerr << endl;
int bestCost = 1<<30;
rep(_,0,3) {
int tempCost = 0;
vector<vi> currSwapsNeeded = swapsNeeded;
for(auto [a,b] : order) {
//cerr << "swapping " << a << ", " << b << endl;
int temp = min(currSwapsNeeded[a][b], currSwapsNeeded[b][a]);
tempCost += temp;
currSwapsNeeded[a][b] -= temp;
currSwapsNeeded[b][a] -= temp;
if (currSwapsNeeded[a][b] == 0 && currSwapsNeeded[b][a] == 0) continue;
if (currSwapsNeeded[a][b] == 0) swap(a, b);
temp = currSwapsNeeded[a][b];
int c = 3 - a - b;
currSwapsNeeded[a][b] = 0;
currSwapsNeeded[b][c] -= temp;
currSwapsNeeded[a][c] += temp;
tempCost += temp;
//cerr << tempCost << endl;
//trav(v, currSwapsNeeded)
// print(v);
}
bestCost = min(bestCost, tempCost);
next_permutation(all(order));
}
return ans + bestCost;
}
