#include <iostream>
#include <string>
#include <cmath>
#include<algorithm>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<iomanip>
#define _USE_MATH_DEFINES
#include <math.h>
#include <functional>
using namespace std;

#define rep(i,x) for(ll i=0;i<x;i++)
#define repn(i,x) for(ll i=1;i<=x;i++)

typedef long long ll;
const ll INF = 1e17;
const ll MOD = 1000000007;
const ll MAX = 4000001;

ll max(ll a, ll b) {
	if (a > b) { return a; }
	return b;
}

ll min(ll a, ll b) {
	if (a > b) { return b; }
	return a;
}

ll gcd(ll a, ll b) {
	if (b == 0) { return a; }
	if (a < b) { return gcd(b, a); }
	return gcd(b, a % b);
}

ll lcm(ll a, ll b) {
	return a / gcd(a, b) * b;
}

struct edge {
	ll ind;
	ll fr;
	ll to;
	ll d;
};

class mint {
    long long x;
public:
    mint(long long x = 0) : x((x% MOD + MOD) % MOD) {}
    mint operator-() const {
        return mint(-x);
    }
    mint& operator+=(const mint& a) {
        if ((x += a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator-=(const mint& a) {
        if ((x += MOD - a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator*=(const  mint& a) {
        (x *= a.x) %= MOD;
        return *this;
    }
    mint operator+(const mint& a) const {
        mint res(*this);
        return res += a;
    }
    mint operator-(const mint& a) const {
        mint res(*this);
        return res -= a;
    }
    mint operator*(const mint& a) const {
        mint res(*this);
        return res *= a;
    }

    mint operator^(const ll& t)const {
        if (!t) return 1;
        mint a = pow(t >> 1);
        a *= a;
        if (t & 1) a *= *this;
        return a;
    }

    mint pow(ll t) const {
        if (!t) return 1;
        mint a = pow(t >> 1);
        a *= a;
        if (t & 1) a *= *this;
        return a;
    }
    // for prime MOD
    mint inv() const {
        return pow(MOD - 2);
    }
    mint& operator/=(const mint& a) {
        return (*this) *= a.inv();
    }
    mint operator/(const mint& a) const {
        mint res(*this);
        return res /= a;
    }

    friend ostream& operator<<(ostream& os, const mint& m) {
        os << m.x;
        return os;
    }
};

//////////////////////////

template<typename T>
struct Segment_Tree {
    typedef function<T(T, T)> F;

    ll n;
    F f;//モノイドとしての演算(最小値、和　など)
    T unit;//単位元

    ll size;
    vector<T> seg;

    Segment_Tree(ll n0, F f0, T unit0) {
        n = n0;
        f = f0;
        unit = unit0;

        size = 1;
        while (size < n) {
            size *= 2;
        }
        seg.assign(2 * size, unit);
    }


    void update(ll k, T x) {//k番目の要素をxに更新
        k += size - 1;
        seg[k] = x;
        while (k > 1) {
            k /= 2;
            seg[k] = f(seg[2 * k], seg[2 * k + 1]);
        }
    }



    T query_prep(ll a, ll b, ll k, ll l, ll r) {//[a,b)とkに対応する区間[l,r)の共通部分でクエリ
        if (b <= l || a >= r) { return unit; }
        if (a <= l && r <= b) { return seg[k]; }

        T v1 = query_prep(a, b, 2 * k, l, (l + r) / 2);
        T v2 = query_prep(a, b, 2 * k + 1, (l + r) / 2, r);
        return f(v1, v2);

    }

    T query(ll a, ll b) {
        return query_prep(a, b, 1, 1, size + 1);
    }

};

ll tento(ll N, vector<ll> A) {
    vector<pair<ll, ll>> p(N + 1);
    repn(i, N) p[i] = { A[i],i };
    sort(++p.begin(), p.end());

    Segment_Tree<ll> sg(N, [](ll a, ll b) {return a + b; }, 0);
    ll ret = 0;
    
    repn(i, N) {
        ll t = p[i].second;
        ret += sg.query(1, t);
        sg.update(t,1);
    }

    ret = N * (N - 1) / 2 - ret;
    return ret;
}


int main() {
    string S;
    cin >> S;
    vector<ll> s[26];

    ll N = S.size();

    repn(i, N) {
        s[S[i-1] - 'a'].push_back(i);
    }

    ll od = 0;
    rep(i, 26) {
        if (s[i].size() % 2 == 1) { od++; }
    }

    if (od > 1) { cout << -1; }
    else {
        vector<ll> p(N + 1);
        rep(i, 26) {
            rep(j, s[i].size()) {
                p[s[i][j]] = s[i][s[i].size() - 1 - j];
                //cout << i << j << s[i][j] << endl;
            }
        }

        vector<ll> a(N + 1,-1);
        ll c = 1;
        repn(i, N) {
            //cout << p[i] << endl;
            if (a[i] != -1) { continue; }

            if (p[i] == i) { a[i] = (N + 1) / 2; }
            else{
                a[i] = c;
                a[p[i]] = N + 1 - c;
                c++;
            }
        }

        //repn(i, N) cout << a[i]<<endl;

        ll ans = tento(N, a);

        cout << ans;
        
    }
    

	system("PAUSE");
}

Measured memory_bytes: 14456