// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define bit(n) (1LL<<(n))
// functions
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(20);}
} fast_io_;

template<typename T>
struct BIT_{
  int n;
  vector<T> bit;
  BIT_(){}
  BIT_(int n_){
    n = n_;
    bit = vector<T>(n+1, 0);
  }
  void add(int a, T w){
    for(int x = a; x < n; x |= (x + 1)){
      bit[x] += w;
    }
  }
  T sum(int a){
    if(a < 0)return 0;
    T res = 0;
    for(int x = a; x >= 0; x = (x & (x + 1)) - 1){
      res += bit[x];
    }
    return res;
  }
  int lower_bound(T w){
    int x = 0;
    int m = 1;
    while(m <= n)m *= 2;
    for(int k = m; k > 0; k /= 2){
      if(x + k <= n && bit[x+k-1] < w){
        w -= bit[x+k-1];
        x += k;
      }
    }
    return x;
  }
};

typedef struct BIT_<int> BITI;
typedef struct BIT_<long long> BITL;

ll calc(string &s){
  vector<int> cnt(26, 0);
  vector<int> idx(sz(s), -1);
  vector<vector<int>> ac(26);
  rep(i, sz(s)){
    idx[i] = cnt[int(s[i] - 'a')];
    ac[int(s[i] - 'a')].pb(i);
    cnt[int(s[i] - 'a')]++;
  }
  int odd = -1;
  vector<int> v1; v1.reserve(sz(s));
  vector<int> v2; v2.reserve(sz(s));
  rep(i, sz(s)){
    int e = int(s[i] - 'a');
    if(idx[i] == cnt[e] - 1 - idx[i])odd = i;
    else{
      if(idx[i] < cnt[e] / 2){
        v1.pb(i);
        v2.pb(ac[e][cnt[e] - 1 - idx[i]]);
      }
    }
  }
  if(odd >= 0)v1.pb(odd);
  while(sz(v2)){
    v1.pb(v2.back());
    v2.pop_back();
  }
  // cerr << v1 << endl;
  vector<int> tr(sz(s)); rep(i, sz(s))tr[v1[i]] = i;
  BITL bt(sz(s));
  ll res = 0;
  rep(i, sz(s)){
    res += bt.sum(sz(s) - 1) - (tr[i] > 0 ? bt.sum(tr[i] - 1): 0);
    bt.add(tr[i], 1);
  }
  return res;
}

int main(int argc, char const* argv[])
{
  string s; cin >> s;
  vector<int> cnt(26, 0);
  rep(i, sz(s))cnt[int(s[i] - 'a')]++;
  int csum = 0;
  rep(i, 26){
    if(cnt[i] & 1)csum++;
  }
  if(csum > 1){
    cout << -1 << endl;
    return 0;
  }
  ll res = calc(s);
  reverse(whole(s));
  res = min(res, calc(s));
  cout << res << endl;
  return 0;
}


Measured memory_bytes: 6424