#include "dna.h"
#include <bits/stdc++.h>
using namespace std;
int n;
vector<array<int, 9> > pre;
template<typename T, size_t s>
array<T, s> operator-(array<T, s> a, array<T, s> const&b){
for(size_t i = 0; i < s; ++i){
a[i] -= b[i];
}
return a;
}
int deco(char const c){
switch(c){
case 'A':
return 0;
case 'T':
return 1;
case 'C':
return 2;
default:
assert(0);
return -1;
}
}
void init(string a, string b) {
n = a.size();
pre.assign(n+1, array<int, 9>{});
for(int i=0; i<n; ++i){
pre[i+1] = pre[i];
++pre[i+1][deco(a[i])*3+deco(b[i])];
}
}
int get_distance(int x, int y) {
auto tmp = pre[y+1] - pre[x];
int ret = 0;
for(int i:{0,1,2}){
const int j = (i+1)%3;
const int x = min(tmp[3*i+j], tmp[3*j+i]);
ret += x;
tmp[3*i+j] -= x;
tmp[3*j+i] -= x;
}
if(tmp[3*0+1] != tmp[3*1+2] || tmp[3*0+1] != tmp[3*2+0]){
return -1;
}
if(tmp[3*1+0] != tmp[3*2+1] || tmp[3*1+0] != tmp[3*0+2]){
return -1;
}
ret += 2*tmp[3*0+1];
ret += 2*tmp[3*0+2];
return ret;
}
