#include "dna.h"
#include "bits/stdc++.h"
using namespace std;
int a[100005], b[100005];
void init(string A, string B)
{
for(int i=0; i<(int)A.length(); i++)
{
if(A[i]=='C') a[i]=1;
else if(A[i]=='T') a[i]=2;
if(B[i]=='C') b[i]=1;
else if(B[i]=='T') b[i]=2;
}
}
int get_distance(int x, int y)
{
int cnt[3][3], cnt1[3]={0,0,0}, cnt2[3]={0,0,0}, num=0, e, ans=0;
memset(cnt, 0, sizeof(cnt));
for(int i=x; i<=y; i++)
{
cnt[a[i]][b[i]]++;
cnt1[a[i]]++;
cnt2[b[i]]++;
}
if(cnt1[0]!=cnt2[0] or cnt1[1]!=cnt2[1] or cnt1[2]!=cnt2[2]) return -1;
for(int i=0; i<3; i++)
for(int j=i+1; j<3; j++)
{
e=min(cnt[i][j], cnt[j][i]);
num+=e;
ans+=max(cnt[i][j], cnt[j][i])-e;
}
return num+ans/3*2;
}
