#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_ON(bit, i) (((bit >> i) & 1) > 0)

typedef long long LL;
template<typename T> std::vector<T> make_v(size_t a){return std::vector<T>(a);}
template<typename T,typename... Ts> auto make_v(size_t a, Ts... ts){ return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}    // C++14
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }

template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}
// 初項s, 交差dのn個の数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
    return n * (2 * s + (n - 1) * d) / 2;
}

// 2のべき乗数かどうか
bool is_power_of_two(long long x) {
    return !(x & (x - 1));
}

// aとbの最大公約数 O(log min(a, b))
long long gcd(long long a, long long b) {
    if (b == 0) { return a; }
    return gcd(b, a % b);
}

// 数列vの最大公約数 O(N log d)
long long gcd(std::vector<long long> &v) {
    long long ans = v[0];
    for (int i = 1; i < v.size(); ++i) {
        ans = gcd(ans, v[i]);
    }
    return ans;
}

// aとbの最小公倍数 O(log min(a, b))
long long lcm(long long a, long long b) {
    long long g = gcd(a, b);
    return a / g * b;
}

const int INF = 1 << 30;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy2 = {0, 1}, dx2 = {1, 0};  // 右，下
const std::vector<int> dy4 = {0, -1, 0, 1}, dx4 = {1, 0, -1, 0};    // 右，上，左，下
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };


using namespace std;

class FenwickTree {
public:
    const unsigned long long n;
    std::vector<long long> v;

    FenwickTree(unsigned long long n) : n(n) {
        this->v.assign(n + 1, 0);
    }

    // sum(v[0, i))
    long long sum(int i) {
        assert(0 <= i && i <= this->n);

        long long s = 0;
        i -= 1;
        while (i >= 0) {
            s += this->v[i];
            i = (i & (i + 1)) - 1;
        }
        return s;
    }

    // sum(v[left, right))
    long long sum(int left, int right) {
        assert(left <= right);
        return this->sum(right) - this->sum(left);
    }

    // v[i] += x(0-origin)
    void add(int i, long long x) {
        assert(i < this->n);

        while (i < this->n) {
            this->v.at(i) += x;
            i |= i + 1;
        }
    }
};

long long inversion_number(const std::vector<long long> &v) {
    long long max_v = *std::max_element(v.begin(), v.end());
    FenwickTree ft(max_v + 10);

    long long ans = 0;
    for (int i = 0; i < v.size(); ++i) {
        ans += i - ft.sum(v[i]);
        ft.add(v[i], 1);
    }
    return ans;
}


LL solve(string S) {
    const int N = S.size();
    unordered_map<char, int> count;
    FOE(c, S) {
        count[c]++;
    }

    int num_odd = 0;
    char center = 0;
    unordered_map<char, int> left;
    FOE(p, count) {
        if (p.second % 2 == 1) {
            num_odd++;
            center = p.first;
        }
        left[p.first] = p.second / 2;
    }

    if (N % 2 == 0 and num_odd > 0) {
        return -1;
    }
    if (N % 2 == 1 and num_odd == 0) {
        return -1;
    }
    if (num_odd > 1) {
        return -1;
    }

    auto order = make_v<LL>(N);
    fill_v(order, -1);
    int no = 0;

    string L;
    // 左の順序を決める
    FOR(i, 0, N) {
        if (left[S[i]] > 0) {
            left[S[i]]--;
            order[i] = no;
            no++;
            L += S[i];
        }
            // 真ん中
        else if (num_odd > 0) {
            if (S[i] == center and left[S[i]] == 0) {
                order[i] = N / 2;
                left[S[i]]--;
            }
        }
    }

    reverse(ALL(L));
    unordered_map<char, deque<int>> pos;
    FOR(i, 0, L.size()) {
        pos[L[i]].emplace_back(i + N);
    }

    // 右の順序を決める
    FOR(i, 0, N) {
        if (order[i] == -1) {
            auto c = S[i];
            order[i] = pos[c].front();
            pos[c].pop_front();
        }
    }

    return inversion_number(order);
}

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

    string S;
    cin >> S;

    print(solve(S));

    return 0;
}

Measured memory_bytes: 5140