#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <vector>
using namespace std;
// BEGIN NO SAD
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
typedef vector<int> vi;
#define f first
#define s second
// END NO SAD
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<vector<ll>> matrix;
int dp[6][100005];
int cnt[3][100005];
void init(string a, string b) {
int n = sz(a);
for(int i = 0; i < n; i++) {
for(int j = 0; j < 3; j++) {
cnt[j][i+1] = cnt[j][i];
}
if(a[i] == 'A') cnt[0][i+1]++;
if(b[i] == 'A') cnt[0][i+1]--;
if(a[i] == 'C') cnt[1][i+1]++;
if(b[i] == 'C') cnt[1][i+1]--;
if(a[i] == 'T') cnt[2][i+1]++;
if(b[i] == 'T') cnt[2][i+1]--;
}
for(int i = 0; i < n; i++) {
for(int j = 0; j < 6; j++) {
dp[j][i+1] = dp[j][i];
}
if(a[i] == 'A' && b[i] == 'C') dp[0][i+1]++;
if(a[i] == 'C' && b[i] == 'A') dp[1][i+1]++;
if(a[i] == 'A' && b[i] == 'T') dp[2][i+1]++;
if(a[i] == 'T' && b[i] == 'A') dp[3][i+1]++;
if(a[i] == 'C' && b[i] == 'T') dp[4][i+1]++;
if(a[i] == 'T' && b[i] == 'C') dp[5][i+1]++;
}
}
int get_distance(int a, int b) {
b++;
if(cnt[0][b] != cnt[0][a]) return -1;
if(cnt[1][b] != cnt[1][a]) return -1;
if(cnt[2][b] != cnt[2][a]) return -1;
int ret = 0;
int tot = 0;
for(int i = 0; i < 6; i++) {
tot += dp[i][b] - dp[i][a];
}
for(int i = 0; i < 6; i += 2) {
int use = min(dp[i][b] - dp[i][a], dp[i+1][b] - dp[i+1][a]);
tot -= 2 * use;
ret += use;
}
assert(tot % 3 == 0);
ret += (tot / 3) * 2;
return ret;
}
/*
void solve() {
}
// what would chika do
// are there edge cases (N=1?)
// are array sizes proper (scaled by proper constant, for example 2* for koosaga tree)
// integer overflow?
// DS reset properly between test cases
// are you doing geometry in floating points
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
solve();
}
*/
