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#pragma GCC optimize "Ofast"
#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>

using namespace std;

#define f first
#define s second
#define sz(s) (int)s.size()
#define all(s) s.begin(), s.end()
#define pb push_back
#define mp make_pair

#define FOR(i, n) for (int i = 0; i < n; i++)

#define ll long long
#define ld long double

#define vi vector<int>
#define vvi vector<vi>

#define ii pair<int, int>
#define vii vector<ii>
#define vvii vector<vii>
#define vviii vector<vector<pair<int, ii>>>
#define vll vector<ll>
#define pll pair<ll, ll>
#define vpll vector<pll>

template <class T>ostream &operator<<(ostream &os, vector<T> &vec){for (T &el : vec){os << el << ' ';}return os;}
template <class T>istream &operator>>(istream &is, vector<T> &vec) {for (T &el : vec){is >> el;}return is;}

template <class T, class G> ostream &operator<<(ostream &os, pair<T, G> para) { os << para.f << ' ' << para.s; return os;}

const ll BIG_INF = 1e18;
const int INF = 1e9 + 7;
// const int mod = 998244353;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define losuj(a, b) uniform_int_distribution<long long>(a, b)(rng)

template <class T>
void setmax(T & a, T b){a = max(a, b);}
template <class T>
void setmin(T & a, T b){a = min(a, b);}

// #define K long double
// #define KK pair<K, K>

string bez(string s, char lit){
    string ret;
    for(auto & u : s){
        if(u != lit){
            ret.push_back(u);
        }
    }
    return ret;
}

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

    ll ans = 0;
    int np = 0;

    FOR(i, 26){
        vi poz;
        FOR(j, sz(s)){
            if(s[j] == ('a' + i)){
                poz.pb(j);
            }
        }

        np += (sz(poz) & 1);
        FOR(j, (sz(poz) + 1) / 2){
            ans += abs(poz[j] - (sz(s) - 1 - poz[sz(poz) - 1 - j]));
        }

        s = bez(s, 'a' + i);
    }

    cout << (np <= 1 ? ans : -1) << '\n';
}

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    int t = 1;
    // cin >> t;

    while(t--) {
        solve();
    }
}