#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORR(i, a, b) for(int i = (a); i > (b); --i)
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define REPR(i, n) for(int i = n; i >= 0; i--)
#define FOREACH(x, a) for(auto &(x) : (a))
#define VECCIN(x)                                                              \
    for(auto &youso_ : (x)) cin >> youso_
#define bitcnt(x) __builtin_popcount(x)
#define lbit(x) __builtin_ffsll(x)
#define rbit(x) __builtin_clzll(x)
#define SZ(x) ((long long)(x).size())
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()
#define cinfast() cin.tie(0), ios::sync_with_stdio(false)
#define PERM(c)                                                                \
    sort(All(c));                                                              \
    for(bool cp = true; cp; cp = next_permutation(All(c)))
#define MKORDER(n)                                                             \
    vector<int> od(n);                                                         \
    iota(All(od), 0LL);

template <typename T = long long> inline T IN() {
    T x;
    cin >> x;
    return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&... tail) {
    cin >> head;
    CIN(move(tail)...);
}
#define CCIN(...)                                                              \
    char __VA_ARGS__;                                                          \
    CIN(__VA_ARGS__)
#define DCIN(...)                                                              \
    double __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define LCIN(...)                                                              \
    long long __VA_ARGS__;                                                     \
    CIN(__VA_ARGS__)
#define SCIN(...)                                                              \
    string __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define Yes(a) cout << (a ? "Yes" : "No") << "\n"
#define YES(a) cout << (a ? "YES" : "NO") << "\n"
#define Printv(v)                                                              \
    {                                                                          \
        FOREACH(x, v) { cout << x << " "; }                                    \
        cout << "\n";                                                          \
    }
template <typename T = string> inline void eputs(T s) {
    cout << s << "\n";
    exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
    std::fill((T *)array, (T *)(array + N), val);
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;

const int INF = 1e9;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const ll LINF = 1e18;
const double PI = atan(1.0) * 4.0;
const ll dw[] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll dh[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793238

// 0-indexed
template <class T> struct BinaryIndexedTree {
    vector<T> data;

    BinaryIndexedTree(int sz) { data.assign(++sz, 0); }

    T sum(int k) {
        T ret = 0;
        for(++k; k > 0; k -= k & -k) ret += data[k];
        return (ret);
    }

    void add(int k, T x) {
        for(++k; k < data.size(); k += k & -k) data[k] += x;
    }
};

template <class T> struct AdditionalBIT : BinaryIndexedTree<T> {
    int curr;

    AdditionalBIT(int sz) : BinaryIndexedTree<T>(sz) {
        curr = 1;
        while(curr <= sz) curr <<= 1;
    }

    int lower_bound(T w) {
        if(w <= 0) return (0);
        int i = 0;
        for(int k = curr; k > 0; k >>= 1) {
            if(i + k < BinaryIndexedTree<T>::data.size() && BinaryIndexedTree<T>::data[i + k] < w) {
                w -= BinaryIndexedTree<T>::data[i + k];
                i += k;
            }
        }
        return (i);
    }
};

VL idxs[26];

signed main() {
    string S;
    cin >> S;
    ll N = S.length();
    REP(i, N) { idxs[S[i] - 'a'].emplace_back(i); }
    ll ocnt = 0;
    char center = '#';
    ll ccnt = 0;
    REP(i, 26) {
        if(idxs[i].size() % 2) {
            ocnt++;
            center = 'a' + i;
            ccnt = idxs[i].size();
        }
    }
    if(ocnt > N % 2) eputs(-1);
    VD od(N, -1);
    ll num = 0;
    VL tmp(26);
    REP(i, N) {
        if(od[i] >= 0) continue;
        if(S[i] == center && tmp[S[i] - 'a'] == ccnt / 2) {
            od[i] = N / 2;
        } else {
            ll r = *idxs[S[i] - 'a'].rbegin();
            idxs[S[i] - 'a'].pop_back();
            od[i] = num;
            od[r] = N - 1 - num;
            num++;
        }
        tmp[S[i] - 'a']++;
    }
    AdditionalBIT<ll> bit(N + 1);
    ll ans = 0;
    REP(i, N) {
        ans += i - bit.sum(od[i]);
        bit.add(od[i], 1);
    }
    cout << ans << "\n";
}


Measured memory_bytes: 5624