#include "dna.h"
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define pb push_back
#define st first
#define nd second
#define all(a) a.begin(), a.end()
#define lg(a) (31-__builtin_clz(a))
const int LIM=1e5+7;
int A[LIM], B[LIM], sum[LIM][3][3];
int n;
void init(string a, string b) {
n=a.size();
rep(i, n) {
if(a[i]=='T') A[i]=1;
else if(a[i]=='C') A[i]=2;
if(b[i]=='T') B[i]=1;
else if(b[i]=='C') B[i]=2;
if(i) {
rep(j, 3) rep(k, 3) sum[i][j][k]=sum[i-1][j][k];
}
++sum[i][A[i]][B[i]];
}
}
int licz(int x, int y, int a, int b) {
if(!x) return sum[y][a][b];
return sum[y][a][b]-sum[x-1][a][b];
}
int get_distance(int x, int y) {
rep(i, 3) {
int a=0, b=0;
rep(j, 3) {
a+=licz(x, y, i, j);
b+=licz(x, y, j, i);
}
if(a!=b) return -1;
}
int ile[3][3], ans=0, ma=0;
rep(i, 3) rep(j, 3) ile[i][j]=licz(x, y, i, j);
rep(i, 3) rep(j, i) {
int p=min(ile[i][j], ile[j][i]);
ans+=p;
ile[i][j]-=p;
ile[j][i]-=p;
ma=max(ma, max(ile[i][j], ile[j][i]));
}
ans+=2*ma;
return ans;
}
