#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h" // define macro "/D__MAI"

using namespace std;
typedef long long int ll;

#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(cnt,l) for(auto cnt=0ll;(cnt)<(l);++(cnt))
#define rrepeat(cnt,l) for(auto cnt=(l)-1;0<=(cnt);--(cnt))
#define iterate(cnt,b,e) for(auto cnt=(b);(cnt)!=(e);++(cnt))
#define MD 1000000007ll
#define PI 3.1415926535897932384626433832795
template<typename T1, typename T2> ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }
template<typename T> T& maxset(T& to, const T& val) { return to = max(to, val); }
template<typename T> T& minset(T& to, const T& val) { return to = min(to, val); }
void bye(string s, int code = 0) { cout << s << endl; exit(code); }
mt19937_64 randdev(8901016);
inline ll rand_range(ll l, ll h) {
    return uniform_int_distribution<ll>(l, h)(randdev);
}

#if defined(_WIN32) || defined(_WIN64)
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#elif __GNUC__
#else
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
namespace {
#define isvisiblechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0; T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc && cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var * sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) { input_integer<int>(var); return *this; }
        inline MaiScanner& operator>>(long long& var) { input_integer<long long>(var); return *this; }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiblechar(cc); cc = getchar_unlocked());
            for (; isvisiblechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
        }
        template<typename IT> void in(IT begin, IT end) { for (auto it = begin; it != end; ++it) *this >> *it; }
    };
    class MaiPrinter {
    public:
        template<typename T>
        void output_integer(T var) {
            if (var == 0) { putchar_unlocked('0'); return; }
            if (var < 0)
                putchar_unlocked('-'),
                var = -var;
            char stack[32]; int stack_p = 0;
            while (var)
                stack[stack_p++] = '0' + (var % 10),
                var /= 10;
            while (stack_p)
                putchar_unlocked(stack[--stack_p]);
        }
        inline MaiPrinter& operator<<(char c) { putchar_unlocked(c); return *this; }
        inline MaiPrinter& operator<<(int var) { output_integer<int>(var); return *this; }
        inline MaiPrinter& operator<<(long long var) { output_integer<long long>(var); return *this; }
        inline MaiPrinter& operator<<(char* str_p) { while (*str_p) putchar_unlocked(*(str_p++)); return *this; }
        inline MaiPrinter& operator<<(const string& str) {
            const char* p = str.c_str();
            const char* l = p + str.size();
            while (p < l) putchar_unlocked(*p++);
            return *this;
        }
        template<typename IT> void join(IT begin, IT end, char sep = '\n') { for (auto it = begin; it != end; ++it) *this << *it << sep; }
    };
}
MaiScanner scanner;
MaiPrinter printer;


template<typename T = ll>
class Bitree {
public:
    int size_;
    vector<T> data_;
    Bitree(int size_) :size_(size_ + 1), data_(size_ + 1) {}

    // 1..rの範囲の値の和を求める．
    T sum(int r) {
        T s = 0;
        while (r) {
            s += data_[r];
            r -= r & -r; //  r&-r と書くことで最下のビットを得る
        }
        return s;
    }
    // l..rの範囲の値の和を求める
    inline T sum(int l, int r) { return sum(r) - sum(l - 1); }
    // idxの要素の値をval増やす
    void add(int idx, T val) {
        while (idx <= size_) {
            data_[idx] += val;
            idx += idx & -idx;
        }
    }
};



ll m, n, kei;
string str;

int main() {

    scanner >> str;
    n = str.size();

    vector<int> ccnt(26);

    repeat(i, n) {
        ccnt[str[i] - 'a'] += 1;
    }
    {
        bool b = true;
        for (int c : ccnt) {
            if (c % 2 == 1) {
                if (b && n % 2 == 1)
                    b = false;
                else
                    bye("-1");
            }
        }
    }
    // vector<vector<int>> encounter(26);
    // repeat(i, n) {
    //     encounter[str[i] - 'a'].push_back(i);
    // }
    vector<vector<int>> numbering(26);
    vector<int> str_half; str_half.reserve(n / 2);
    int cnt = 1;

    // left
    repeat(i, n) {
        int c = str[i] - 'a';
        if (numbering[c].size() < ccnt[c] / 2) {
            numbering[c].push_back(cnt++);
            str_half.push_back(c);
        }
    }
    // center
    repeat(c, 26) {
        if (ccnt[c] % 2 == 1)
            numbering[c].push_back(cnt++);
    }
    //right
    vector<int> recount(26);
    rrepeat(i, n/2) {
        int c = str_half[i];
        numbering[c].push_back(cnt++);
    }

    fill(ALL(recount), 0);
    vector<int> perm(n);

    repeat(i, n) {
        int c = str[i] - 'a';
        perm[i] = numbering[c][recount[c]++];
    }


    Bitree<ll> bit(n);
    ll ans = 0;

    //debugv(perm)

    for (int p : perm) {
        ll z = bit.sum(p, n);
        bit.add(p, 1);
        ans += z;
    }


    cout << ans << endl;


    return 0;
}

Measured memory_bytes: 4228