#include <bits/stdc++.h>
using namespace std;
int n, c[100001][3][3];
int val(char x) {
return x == 'A' ? 0 : x == 'T' ? 1 : 2;
}
void init(string a, string b) {
n = a.length();
for (int i = 0; i < n; ++i) {
++c[i + 1][val(a[i])][val(b[i])];
for (int j = 0; j < 3; ++j)
for (int k = 0; k < 3; ++k)
c[i + 1][j][k] += c[i][j][k];
}
}
int get_distance(int x, int y) {
int left = y - x + 1, swaps = 0;
int cur[3][3];
for (int i = 0; i < 3; ++i)
for (int j = 0; j < 3; ++j)
cur[i][j] = c[y + 1][i][j] - c[x][i][j];
for (int i = 0; i < 3; ++i)
left -= cur[i][i];
for (int i = 0; i < 3; ++i)
for (int j = i + 1; j < 3; ++j) {
int off = min(cur[i][j], cur[j][i]);
cur[i][j] -= off, cur[j][i] -= off;
left -= 2 * off, swaps += off;
}
int a = n, b = n;
for (int i = 0; i < 3; ++i)
a = min(a, cur[i][(i + 1) % 3]), b = min(b, cur[(i + 1) % 3][i]);
for (int i = 0; i < 3; ++i)
cur[i][(i + 1) % 3] -= a, cur[(i + 1) % 3][i] -= b;
left -= 3 * (a + b), swaps += 2 * (a + b);
if (left)
return -1;
return swaps;
}
