#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a,b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a,b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
/*
*/
const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
#include "dna.h"
string s,t;
int f(char ch){
if(ch == 'A') return 0;
if(ch == 'C') return 1;
if(ch == 'T') return 2;
assert(0);
return -1;
}
void init(std::string a, std::string b) {
s = a, t = b;
}
int get_distance(int l, int r) {
vector<int> cnt(3);
int c[3][3];
memset(c,0,sizeof c);
for(int i = l; i <= r; ++i){
cnt[f(s[i])]++, cnt[f(t[i])]--;
if(s[i] != t[i]){
c[f(s[i])][f(t[i])]++;
}
}
rep(i,3) if(cnt[i]) return -1;
int ans = 0;
rep(i,3){
for(int j = i+1; j < 3; ++j){
int mn = min(c[i][j],c[j][i]);
c[i][j] -= mn, c[j][i] -= mn;
ans += mn;
}
}
int mn = inf1, mx = -inf1;
rep(i,3){
rep(j,3){
if(c[i][j]){
amin(mn,c[i][j]);
amax(mx,c[i][j]);
}
}
}
if(mn <= mx){
assert(mn == mx);
ans += 2*mn;
}
return ans;
}
