#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <bitset>
#include <vector>
#include <algorithm>
#include <random>
#include <map>
#include <set>
#include <deque>
#include <cassert>
const int N = 2e5 + 7, A = 26, MOD = 1e9+7, C = 2;
using namespace std;

int lb(int a) {
    return a & (-a);
}

struct Fenwick {
    int f[N];
    void add(int i, int val) {
        for (i; i < N; i += lb(i)) {
            f[i] += val;
        }
    }
    int get(int i) {
        int ans = 0;
        for (i; i > 0; i -= lb(i)) {
            ans += f[i];
        }
        return ans;
    }
};
Fenwick F;

string s,order;

bool pos[N];
int cnt[A],cnt2[A], nxt[N], cur[A], prv[A], n;


signed main()
{
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
#else
    std::ios::sync_with_stdio(false);
    cin.tie(0);
#endif
    cin >> s;
    n = s.size();
    for (int i = 0; i < n; i++) {
        cnt[s[i] - 'a']++;
        F.add(i + 1, 1);
    }
    int cnt_nechet = 0;
    for (int i = 0; i < A; i++) {
        if (cnt[i] % 2) {
            cnt_nechet++;
        }
    }
    if (cnt_nechet > 1) {
        cout << -1;
        return 0;
    }
    for (int i = 0; i < n; i++) {
        cnt2[s[i] - 'a']++;
        if (cnt2[s[i] - 'a'] > cnt[s[i] - 'a'] / 2 + cnt[s[i] - 'a'] % 2) {
            pos[i] = 1;
            order.push_back(s[i]);
        }
        nxt[i] = -1;
    }
    reverse(order.begin(), order.end());
    if (cnt_nechet == 1) {
        for (int i = 0; i < A; i++) {
            if (cnt[i] & 1) {
                order.push_back(i + 'a');
            }
        }
    }
    for (int i = 0; i < A; i++) {
        cur[i] = -1;
        prv[i] = -1;
    }
    for (int i = 0; i < n; i++) {
        if (prv[s[i] - 'a'] == -1) {
            prv[s[i] - 'a'] = i;
            cur[s[i] - 'a'] = i;
        }
        else {
            nxt[prv[s[i] - 'a']] = i;
            prv[s[i] - 'a'] = i;
        }
    }
    long long ans = 0;
    for (int i = 0; i < order.size(); i++) {
        int c = order[i] - 'a';
        int ind = cur[c];
        int swap_num = F.get(ind);
        ans += swap_num;
        F.add(ind + 1, -1);
        cur[c] = nxt[ind];
    }
    cout << ans;
}