#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define pb(e) push_back(e)
#define sv(a) sort(a.begin(),a.end())
#define sa(a,n) sort(a,a+n)
#define mp(a,b) make_pair(a,b)
#define vf first
#define vs second
#define ar array
#define all(x) x.begin(),x.end()
const int inf = 0x3f3f3f3f;
const int mod = 1000000007;
const double PI=3.14159265358979323846264338327950288419716939937510582097494459230;
bool remender(ll a , ll b){return a%b;}
const int N = 100002;
int cnt[N][3][3];
void init(std::string a, std::string b) {
int n = a.size();
memset(cnt,0,sizeof cnt);
for(int i = 0; i < n; i++){
if(i){
for(int j = 0; j < 3; j++){
for(int k = 0; k < 3; k++){
cnt[i][j][k] = cnt[i-1][j][k];
}
}
}
if(a[i] != b[i]){
int x , y;
if(a[i] == 'A')x = 0;
else if(a[i] == 'T')x = 1;
else x = 2;
if(b[i] == 'A')y = 0;
else if(b[i] == 'T')y = 1;
else y = 2;
cnt[i][x][y]++;
}
}
}
int get_distance(int x, int y) {
int a[3][3];
for(int i = 0; i < 3; i++){
for(int j = 0; j < 3; j++){
a[i][j] = cnt[y][i][j];
if(x > 0)a[i][j] -= cnt[x-1][i][j];
}
}
int ans = 0;
int t = min(a[0][1] , a[1][0]);
ans += t;
a[0][1] -= t;
a[1][0] -= t;
t = min(a[0][2] , a[2][0]);
ans += t;
a[0][2] -= t;
a[2][0] -= t;
t = min(a[1][2] , a[2][1]);
ans += t;
a[1][2] -= t;
a[2][1] -= t;
int r0 = a[0][1] + a[0][2] , r1 = a[1][0] + a[1][2] , r2 = a[2][0] + a[2][1];
if(r0 == r1 && r1 == r2){
ans += r0 + r0;
}
else ans = -1;
return ans;
}
/*
int main(){
int n , q;
cin >> n >> q;
string a , b;
cin >> a >> b;
init(a,b);
while(q--){
int x , y;
cin >> x >> y;
cout << get_distance(x , y);
}
}
*/
