/* ---------- STL Libraries ---------- */

// IO library
#include <cstdio>
#include <fstream>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>

// container library
#include <array>
#include <bitset>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

/* ---------- Namespace ---------- */

using namespace std;

/* ---------- Type Abbreviation ---------- */

template <typename T>
using V = vector<T>;
template <typename T, typename U>
using P = pair<T, U>;
template <typename T>
using PQ = priority_queue<T>;
template <typename T>
using GPQ = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;

#define fst first
#define snd second
#define pb push_back
#define mp make_pair
#define mt make_tuple

/* ---------- conversion ---------- */

#define INT(c) static_cast<int>(c)
#define CHAR(n) static_cast<char>(n)
#define LL(n) static_cast<ll>(n)
#define DOUBLE(n) static_cast<double>(n)

/* ---------- container ---------- */

#define ALL(v) (v).begin(), (v).end()
#define SIZE(v) (LL((v).size()))

#define FIND(v, k) (v).find(k) != (v).end()
#define VFIND(v, k) find(ALL(v), k) != (v).end()

#define gsort(b, e) sort(b, e, greater<decltype(*b)>())
#define SORT(v) sort(ALL(v))
#define GSORT(v) gsort(ALL(v))

/* ---------- repetition ---------- */

#define FOR(i, a, b) for (ll i = (a); i <= (b); ++i)
#define RFOR(i, a, b) for (ll i = (a); i >= (b); --i)

/* ----------- debug ---------- */

template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
    os << "[";
    for (auto vv : v)
        os << vv << ",";
    return os << "]";
}

template <class T>
ostream& operator<<(ostream& os, set<T> v) {
    os << "[";
    for (auto vv : v)
        os << vv << ",";
    return os << "]";
}

template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> p) {
    return os << "(" << p.fst << "," << p.snd << ")";
}

/* ---------- Constants ---------- */

// const ll MOD = 1e9 + 7;
// const int INF = 1 << 25;
// const ll INF = 1LL << 50;
// const double PI = acos(-1);
// const double EPS = 1e-10;
// const ll dx[4] = {0, -1, 1, 0};
// const ll dy[4] = {-1, 0, 0, 1};

/* ---------- Short Functions ---------- */

template <typename T>
T sq(T a) {
    return a * a;
}

template <typename T>
T gcd(T a, T b) {
    if (a > b) return gcd(b, a);
    return a == 0 ? b : gcd(b % a, a);
}

template <typename T, typename U>
T mypow(T b, U n) {
    if (n == 0) return 1;
    if (n == 1) return n /* % MOD */;
    if (n % 2 == 0) {
        return mypow(sq(b) /* % MOD */, n / 2);
    } else {
        return mypow(b, n - 1) * b /* % MOD */;
    }
}

ll pcnt(ll b) {
    return __builtin_popcountll(b);
}

/* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */

// #define DEBUG
// #define DEBUG_CASE_NUM 3

class BIT {
public:
    // 要素数N、値vで初期化
    BIT(ll N, ll v) : V_NUM(N) {
        data.resize(N);
        fill(ALL(data), v);
    }

    // [1, i]の総和を求める
    ll query(ll i) {
        ll ret = 0;
        while (i > 0) {
            ret += data[i];
            i -= (i & -i);
        }
        return ret;
    }

    // data[i]にv可算
    void update(ll i, ll v) {
        while (i < V_NUM) {
            data[i] += v;
            i += (i & -i);
        }
    }

    ll V_NUM;
    V<ll> data;
};

ll bubble(string from, string to) {
    ll N = SIZE(from);
    queue<ll> cidx[26];
    FOR(i, 0, N - 1) {
        cidx[from[i] - 'a'].push(N - i);
    }

    V<ll> idx(N);
    FOR(i, 0, N - 1) {
        idx[i] = cidx[to[i] - 'a'].front();
        cidx[to[i] - 'a'].pop();
    }

    BIT bit(N + 1, 0);

    ll ans = 0;
    FOR(i, 0, N - 1) {
        ans += bit.query(idx[i]);
        bit.update(idx[i], 1);
    }

    return ans;
}

void solve() {
    string S;
    cin >> S;

    V<ll> cnt(26, 0);
    for (char c : S) {
        cnt[c - 'a']++;
    }

    ll oddcnt = 0;
    FOR(i, 0, 25) {
        oddcnt += cnt[i] % 2;
    }

    if (oddcnt > 1) {
        cout << -1 << endl;
        return;
    }

    string pre;
    V<ll> appear(26, 0);
    for (char c : S) {
        if (appear[c - 'a'] < cnt[c - 'a'] / 2) {
            pre.pb(c);
            appear[c - 'a']++;
        }
    }

    string to = pre;
    FOR(i, 0, 25) {
        if (cnt[i] % 2 > 0) {
            to.pb(CHAR(i + 'a'));
        }
    }

    reverse(ALL(pre));
    to += pre;

    cout << bubble(S, to) << endl;

    return;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // cout << fixed << setprecision(10);

#ifdef DEBUG
    freopen("input.txt", "r", stdin);
    FOR(_, 1, DEBUG_CASE_NUM) {
        solve();
        cout << "++++++++++" << endl;
    }
#else
    solve();
#endif

    return 0;
}


Measured memory_bytes: 6036