#include <iostream>
#include <string>
#include <cassert>
using namespace std;
const int MAX = 4;
struct Matrix
{
int a[MAX][MAX];
Matrix()
{
for (int i=0;i<MAX;i++)
for (int j=0;j<MAX;j++)
a[i][j] = 0;
}
void add(const Matrix &o)
{
for (int i=0;i<MAX;i++)
for (int j=0;j<MAX;j++)
a[i][j] += o.a[i][j];
}
void sub(const Matrix &o)
{
for (int i=0;i<MAX;i++)
for (int j=0;j<MAX;j++)
a[i][j] -= o.a[i][j];
}
int swapdistance() const
{
int mtot = 0;
int si[MAX];
for (int i=0;i<MAX;i++)
si[i] = 0;
for (int i=0;i<MAX;i++)
for (int j=0;j<MAX;j++)
{
mtot += a[i][j];
si[i] += a[i][j];
si[j] -= a[i][j];
}
for (int node=0;node<MAX;node++)
if (si[node])
return -1;
Matrix aux = *this;
int cycles = 0;
for (int i=0;i<MAX;i++)
{
cycles += aux.a[i][i];
aux.a[i][i] = 0;
}
for (int i=0;i<MAX;i++)
for (int j=0;j<i;j++)
{
int c = min(aux.a[i][j], aux.a[j][i]);
cycles += c;
aux.a[i][j] -= c;
aux.a[j][i] -= c;
}
for (int i=0;i<MAX;i++)
for (int j=0;j<i;j++)
for (int k=0;k<j;k++)
{
int c;
c = min(aux.a[i][j], min(aux.a[j][k], aux.a[k][i])); cycles += c; aux.a[i][j] -= c; aux.a[j][k] -= c; aux.a[k][i] -= c;;
c = min(aux.a[i][k], min(aux.a[k][j], aux.a[j][i])); cycles += c; aux.a[i][k] -= c; aux.a[k][j] -= c; aux.a[j][i] -= c;;
}
int remainingEdges = 0;
for (int i=0;i<MAX;i++)
for (int j=0;j<MAX;j++)
remainingEdges += aux.a[i][j];
assert(remainingEdges % MAX == 0);
cycles += remainingEdges / MAX;
return mtot - cycles;
}
};
const int MAXN = 250000;
Matrix prefix[MAXN+1];
void prefixAdd(int pos, const Matrix &value) {
assert(0 <= pos);
assert(pos < MAXN);
pos++;
prefix[pos].add(prefix[pos-1]);
prefix[pos].add(value);
}
Matrix prefixQuery(int pos) {
assert(0 <= pos);
assert(pos <= MAXN);
Matrix ret;
ret.add(prefix[pos]);
return ret;
}
int charValues[256];
string globalA, globalB;
void init(string a, string b)
{
globalA = a;
globalB = b;
charValues['A'] = 0;
charValues['T'] = 1;
charValues['C'] = 2;
charValues['G'] = 3;
Matrix mat;
for (int i=0;i<int(a.size());i++)
{
int x = charValues[int(a[i])];
int y = charValues[int(b[i])];
mat.a[x][y] = 1;
prefixAdd(i, mat);
mat.a[x][y] = 0;
}
}
int get_distance(int i,int j)
{
Matrix mat = prefixQuery(j+1);
mat.sub(prefix[i]);
return mat.swapdistance();
}
