static long Solve()
{
var S = ReadLine();
var s = S.Select(c => c - 'a').ToArray();
int N = S.Length, odd = 0, mid = -1;
var cnt = new int[26];
foreach (var c in s)
{
cnt[c]++;
}
for (var c = 0; c < 26; c++)
{
if (cnt[c] % 2 == 1)
{
mid = c; odd++;
}
cnt[c] /= 2;
}
if (odd > 1)
{
return(-1);
}
var left = new List <int>();
foreach (var c in s)
{
if (cnt[c] > 0)
{
cnt[c]--; left.Add(c);
}
}
int[] t = new int[N], ind = new int[26], p = new int[N];
for (var i = 0; i < left.Count; i++)
{
t[N - 1 - i] = t[i] = left[i];
}
if (mid >= 0)
{
t[N / 2] = mid;
}
for (var i = 0; i < N; i++)
{
var c = s[i];
while (t[ind[c]] != c)
{
ind[c]++;
}
p[i] = ind[c]++;
}
return(BIT.Inversion(p));
}
