#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define FOR(i,x,y) for(ll i = x; i<y; i++)
string a, b;
ll prefab[100001], prefac[100001], prefba[100001], prefbc[100001],prefca[100001],prefcb[100001], prefsame[100001], pref1a[100001], pref1b[100001], pref1c[100001],pref2a[100001], pref2b[100001], pref2c[100001];
void init(string A, string B){
for (auto&i : A){
if (i=='A') a += 'a';
if (i=='T') a += 'b';
if (i=='C') a += 'c';
}
for (auto&i : B){
if (i=='A') b += 'a';
if (i=='T') b += 'b';
if (i=='C') b += 'c';
}
ll n = a.size();
pref1a[0] = 0;
pref1b[0] = 0;
pref1c[0] = 0;
pref2a[0] = 0;
pref2b[0] = 0;
pref2c[0] = 0;
prefab[0] = 0;
prefac[0] = 0;
prefba[0] = 0;
prefbc[0] = 0;
prefca[0] = 0;
prefcb[0] = 0;
prefsame[0] = 0;
if (a[0] == 'a') pref1a[0] = 1;
else if (a[0] == 'b') pref1b[0] = 1;
else pref1c[0] = 1;
if (b[0] == 'a') pref2a[0] = 1;
else if (b[0] == 'b') pref2b[0] = 1;
else pref2c[0] = 1;
if (a[0] == b[0]) prefsame[0] = 1;
if (a[0] == 'a' && b[0] == 'b') prefab[0] = 1;
if (a[0] == 'a' && b[0] == 'c') prefac[0] = 1;
if (a[0] == 'b' && b[0] == 'a') prefba[0] = 1;
if (a[0] == 'b' && b[0] == 'c') prefbc[0] = 1;
if (a[0] == 'c' && b[0] == 'a') prefca[0] = 1;
if (a[0] == 'c' && b[0] == 'b') prefcb[0] = 1;
ll c = 0;
FOR(i,1,n){
c = 0;
if (a[i] == 'a') pref1a[i] = 1;
else if (a[i] == 'b') pref1b[i] = 1;
else pref1c[i] = 1;
if (b[i] == 'a') pref2a[i] = 1;
else if (b[i] == 'b') pref2b[i] = 1;
else pref2c[i] = 1;
if (a[i] == b[i]) prefsame[i] = 1;
if (a[i] == 'a' && b[i] == 'b') prefab[i] = 1;
if (a[i] == 'a' && b[i] == 'c') prefac[i] = 1;
if (a[i] == 'b' && b[i] == 'a') prefba[i] = 1;
if (a[i] == 'b' && b[i] == 'c') prefbc[i] = 1;
if (a[i] == 'c' && b[i] == 'a') prefca[i] = 1;
if (a[i] == 'c' && b[i] == 'b') prefcb[i] = 1;
pref1a[i] += pref1a[i-1];
pref1b[i] += pref1b[i-1];
pref1c[i] += pref1c[i-1];
pref2a[i] += pref2a[i-1];
pref2b[i] += pref2b[i-1];
pref2c[i] += pref2c[i-1];
prefab[i] += prefab[i-1];
prefac[i] += prefac[i-1];
prefba[i] += prefba[i-1];
prefbc[i] += prefbc[i-1];
prefca[i] += prefca[i-1];
prefcb[i] += prefcb[i-1];
prefsame[i] += prefsame[i-1];
}
}
int get_distance(int x, int y){
if (!(pref1a[y] - pref1a[x] + (a[x]=='a') == pref2a[y] - pref2a[x] + (b[x]=='a') && pref1b[y] - pref1b[x] + (a[x]=='b') == pref2b[y] - pref2b[x] + (b[x]=='b') && pref1c[y] - pref1c[x] + (a[x]=='c') == pref2c[y] - pref2c[x] + (b[x]=='c'))){
return -1;
}
ll ab = prefab[y] - prefab[x] + (a[x] == 'a' && b[x] == 'b');
ll ac = prefac[y] - prefac[x] + (a[x] == 'a' && b[x] == 'c');
ll ba = prefba[y] - prefba[x] + (a[x] == 'b' && b[x] == 'a');
ll bc = prefbc[y] - prefbc[x] + (a[x] == 'b' && b[x] == 'c');
ll ca = prefca[y] - prefca[x] + (a[x] == 'c' && b[x] == 'a');
ll cb = prefcb[y] - prefcb[x] + (a[x] == 'c' && b[x] == 'b');
ll ans = 0;
ll sum = ab+ac+ba+bc+ca+cb;
sum -= min(ab,ba)*2;
sum -= min(ac,ca)*2;
sum -= min(bc,cb)*2;
ans += min(ab,ba) + min(ac,ca) + min(bc,cb);
ans += sum/3 * 2;
return ans;
}
