#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit(b) (1ll << (b))
#define uniq(v) (v).erase(unique(all(v)), (v).end())
#define rsort(v) sort(all(v)); reverse(all(v))

using namespace std;

using i32 = int;
using i64 = long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() { cout << "Yes" << '\n'; exit(0); }
inline void no() { cout << "-1" << '\n'; exit(0); }
inline i64 gcd(i64 a, i64 b) { if (min(a, b) == 0) return max(a, b); if (a % b == 0) return b; return gcd(b, a % b); }
inline i64 lcm(i64 a, i64 b) { return a / gcd(a, b) * b; }
void solve(); int main() { ios::sync_with_stdio(0); cin.tie(0); cout << fixed << setprecision(16); solve(); return 0; }
template<typename T> class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template<typename T> class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template<typename T> inline void amax(T &x, T y) { if (x < y) x = y; }
template<typename T> inline void amin(T &x, T y) { if (x > y) x = y; }
template<typename T> inline T power(T x, i64 n) { T r = 1; while (n > 0) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; }
template<typename T> istream& operator>>(istream &is, vector<T> &v) { for (auto &x : v) is >> x; return is; }
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { rep(i, v.size()) { if (i) os << ' '; os << v[i]; } return os; }

struct FenwickTree {
  vi32 v;
  FenwickTree(int n) {
    v = vi32(n);
  }
  void add(int i, int x) {
    for (i++; i <= v.size(); i += i & -i) v[i - 1] += x;
  }
  int sum(int i) {
    int r = 0;
    for (; i >= 1; i -= i & -i) r += v[i - 1];
    return r;
  }
};

template<typename Ord> i64 crossing(vector<Ord> v) {
  auto copy = v;
  sort(all(copy));
  uniq(v);
  map<Ord, i32> mp;
  rep(i, copy.size()) mp[copy[i]] = i;
  rep(i, v.size()) v[i] = mp[v[i]];
  FenwickTree ft(v.size());
  i64 ret = 0;
  rep(i, v.size()) {
    ret += i - ft.sum(v[i] + 1);
    ft.add(v[i], 1);
  }
  return ret;
}

void solve() {
  string s;
  cin >> s;
  int n = s.size();
  int cnt[26];
  rep(i, 26) cnt[i] = 0;
  {
    rep(i, n) cnt[s[i] - 'a']++;
    if (n % 2 == 0) rep(i, 26) if (cnt[i] % 2 != 0) no();
    if (n % 2 == 1) {
      bool f = false;
      int c;
      rep(i, 26) {
        if (!f && cnt[i] % 2 == 1) { f = true, c = i; }
        else if (f && cnt[i] % 2 == 1) no();
      }
      if (!f) no();
      int ct = 0;
      rep(i, n / 2) if (s[i] - 'a' == c) ct++;
      if (ct > cnt[c] / 2) reverse(all(s));
    }
  }
  i64 ans = 0;
  vi32 indices[26];
  {
    vi32 nums(n);
    vi32 chr(26);
    int lef = 0, mid = n / 2, rig = (n + 1) / 2;
    rep(i, n) {
      int idx = s[i] - 'a';
      int c = cnt[idx];
      chr[idx]++;
      if (c % 2 == 0) {
        if (chr[idx] <= c / 2) { indices[idx].push_back(lef); nums[i] = lef++; }
        else nums[i] = rig++;
      } else {
        if (chr[idx] <= c / 2) { indices[idx].push_back(lef); nums[i] = lef++; }
        else if (chr[idx] == c / 2 + 1) nums[i] = mid;
        else nums[i] = rig++;
      }
    }
    ans += crossing(nums);
  }
  {
    vi32 res;
    vi32 nums[3];

    string t = s;
    reverse(all(t));
    vi32 ind(26);
    vi32 chr(26);
    int lef = n / 2;

    rep(i, n) {
      int idx = t[i] - 'a';
      int c = cnt[idx];
      chr[idx]++;
      if (c % 2 == 0) {
        if (chr[idx] <= c / 2) nums[2].push_back(n - 1 - indices[idx][ind[idx]++]);
        else nums[0].push_back(--lef);
      } else {
        if (chr[idx] <= c / 2) nums[2].push_back(n - 1 - indices[idx][ind[idx]++]);
        else if (chr[idx] == c / 2 + 1) nums[1].push_back(n / 2);
        else nums[0].push_back(--lef);
      }
    }

    rep(i, 3) reverse(all(nums[i]));
    rep(i, 3) res.insert(res.end(), all(nums[i]));
    ans += crossing(res);
  }
  cout << ans << '\n';
}


Measured memory_bytes: 14456