#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <class S, class T>
ostream& operator<<(ostream& out, const pair<S, T>& o) {
    out << "(" << o.first << "," << o.second << ")";
    return out;
}
template <class T>
ostream& operator<<(ostream& out, const vector<T>& V) {
    for (int i = 0; i < V.size(); i++) {
        out << V[i];
        if (i != V.size() - 1) out << " ";
    }
    return out;
}
template <class T>
ostream& operator<<(ostream& out, const vector<vector<T> >& Mat) {
    for (int i = 0; i < Mat.size(); i++) {
        if (i != 0) out << endl;
        out << Mat[i];
    }
    return out;
}
template <class S, class T>
ostream& operator<<(ostream& out, const map<S, T>& mp) {
    out << "{ ";
    for (auto it = mp.begin(); it != mp.end(); it++) {
        out << it->first << ":" << it->second;
        if (mp.size() - 1 != distance(mp.begin(), it)) out << ", ";
    }
    out << " }";
    return out;
}
template <typename T>
vector<T> make_v(size_t a) {
    return vector<T>(a);
}
template <typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
    return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T& t, const V& v) {
    t = v;
}
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T& t, const V& v) {
    for (auto& e : t) fill_v(e, v);
}
/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

/*
 BIT 1-index
 add : x に valを加算
 sum : [1,x] の総和を出力
 */
struct BIT {
    ll N;
    vector<ll> bit;
    BIT(ll N) : N(N) {
        /* BITは[1..N]で扱う */
        bit.resize(N + 1, 0);
    }

    void add(int x, ll val) {
        while (x <= N) {
            bit[x] += val;
            x += x & -x;
        }
    }

    ll sum(int x) {
        ll ret = 0;
        if (x == 0) return ret;
        while (x) {
            ret += bit[x];
            x &= (x - 1);
        }
        return (ret);
    }
    // [l,r]
    ll sum(int l, int r) { return sum(r) - sum(l - 1); }
};

template <class Type>
Type solve(Type res = Type()) {
    string S;
    cin >> S;
    map<char, int> mp;
    for (auto c : S) mp[c-'a']++;
    int odd_num = 0;
    for (auto p : mp) {
        if (p.second % 2 == 1) {
            odd_num++;
        }
    }
    if (odd_num >= 2) return -1;
    if (S.length() % 2 != odd_num) return -1;

    string L, M, R;
    vector<int> id(26);
    vector<int> state(S.length());
    for (int i = 0; i < (int)S.length(); i++) {
        if (mp[S[i] - 'a'] & 1) {
            if (id[S[i] - 'a'] < mp[S[i] - 'a'] / 2) {
                state[i] = 0;
            } else if (id[S[i] - 'a'] == mp[S[i] - 'a'] / 2) {
                state[i] = 1;
            } else {
                state[i] = 2;
            }
        } else {
            if (id[S[i] - 'a'] < mp[S[i] - 'a'] / 2) {
                state[i] = 0;
            } else {
                state[i] = 2;
            }
        }
        if(state[i] == 0){
            L += S[i];
        }else if(state[i] == 1){
            M += S[i];
        }else{
            R += S[i];
        }
        id[S[i]-'a']++;
    }
    reverse(L.begin(),L.end());

    deque<int> Lid[26];
    for(int i = 0; i < (int)L.length();i++){
        Lid[L[i]-'a'].push_front(i+S.length()/2 + (S.length()&1));
    }

    vector<int> Rid;
    for(int i = 0; i < (int)R.length();i++){
        Rid.emplace_back(Lid[R[i]-'a'].back());
        Lid[R[i]-'a'].pop_back();
    }

    vector<int> move_id;
    int id1 = 0,id2 = 0;
    for(int i = 0; i < (int)S.length();i++){
        if(state[i] == 0){
            move_id.emplace_back(id1++);
        }else if(state[i] == 1){
            move_id.emplace_back((int)S.length()/2);
        }else{
            move_id.emplace_back(Rid[id2++]);
        }
    }

    BIT bit(S.length());
    for(int i = 0; i < move_id.size();i++){
        res += i - bit.sum(move_id[i]+1);
        bit.add(move_id[i]+1,1);
    }
    return res;
}
int main(void) {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // solve<ll>(0);
    cout << fixed << setprecision(12) << solve<ll>() << endl;
    return 0;
}

Measured memory_bytes: 7868