#include "dna.h"
#include<bits/stdc++.h>
using namespace std;
#define sz(x) (int)x.size()
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define pb push_back
#define lowb(x) (x&(-x))
#define ALL(_x) _x.begin(),_x.end()
#define pii pair<int,int>
#define f first
#define s second
#define SORT_UNIQUE(x) sort(ALL(x)),x.erase(unique(ALL(x)),x.end())
#define ll long long
#define MNTO(x,y) x=min(x,y)
#define MXTO(x,y) x=max(x,y)
const int maxn=2e5+5;
const int INF=0x3f3f3f3f;
string a,b;
#define REP(i,n) for(int i=0;i<n;i++)
int to(char c){
if(c=='A') return 0;
if(c=='T') return 1;
return 2;
}
void init(std::string A, std::string B) {
a=A,b=B;
}
int get_distance(int x, int y) {
int cnt=0;
int c[3]={0,0,0};
for(int i=x;i<=y;i++){
c[to(a[i])]++;
c[to(b[i])]--;
if(a[i]!=b[i]){
++cnt;
}
}
REP(i,3){
if(c[i]){
return -1;
}
}
return (cnt+1)/2;
}
