#include <bits/stdc++.h>
#define int long long int
#define mod(x) ((x % MOD) + MOD) % MOD
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define FORE(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for(int i=(b)-1;i>=(a);--i)
#define RFORE(i,a,b) for(int i=(b);i>=(a);--i)
#define REP(i,n) FOR(i,0,n)
#define ALL(c) (c).begin(),(c).end()
#define RALL(c) (c).rbegin(),(c).rend()
#define SORT(c) sort(ALL(c))
#define RSORT(c) sort(RALL(c))
#define SZ(c) (int)((c).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define LB(c,x) (int)(lower_bound(ALL(c),x)-(c).begin())
#define UB(c,x) (int)(upper_bound(ALL(c),x)-(c).begin())
#define COUNT(c,x) (UB(c,x)-LB(c,x))
#define UNIQUE(c) SORT(c); (c).erase(unique(ALL(c)),(c).end());
#define COPY(c1,c2) copy(ALL(c1),(c2).begin())
#define EXIST(s,e) (bool)((s).find(e)!=(s).end())
#define PB push_back
#define MP make_pair
#define DEL(v) decltype(v)().swap(v)
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
using namespace std;
template<typename T1, typename T2> using P = pair<T1,T2>;
template<typename T> using V = vector<T>;
struct edge { int from, to; int cost; };
bool operator< (const edge &edge1, const edge &edge2) { return edge1.cost < edge2.cost; };
const int INF = 1e18;
const int MOD = 1e9+7;

template<typename T> ostream& operator << (ostream& s, const V<T>& v) {
   s << "[";
   for (int i = 0; i < v.size(); i++) { s << v[i]; if (i < v.size() - 1) s << " "; }
   s << "]";
   return s;
}
template<typename T1, typename T2> ostream& operator << (ostream& s, const map<T1,T2>& m) {
   s << "{";
   for (auto i = m.begin(); i != m.end(); ++i) {
      s << i->first << ":" << i->second;
      if (next(i) != m.end()) s << ", ";
   }
   s << "}";
   return s;
}

template<typename T> class BIT
{
   private:
      vector<T> bit;
      int len;
   public:
      BIT(int n) {
         len = n+1;
         bit.resize(len);
      }
      void add(int i, T x) {
         i += 1;
         while (i < len) {
            bit[i] += x;
            i += i & -i;
         }
      }
      int sum(int i) {
         i += 1;
         T s = 0;
         while (i > 0) {
            s += bit[i];
            i -= i & -i;
         }
         return s;
      }
};

int inversionP(const vector<int>& p) {
   int N = p.size();
   BIT<int> bit(N);
   int res = 0;
   for (int i = 0; i < N; i++) {
      res += i - bit.sum(p[i]);
      bit.add(p[i], 1);
   }
   return res;
}

signed main()
{
   string S; cin >> S;
   int N = SZ(S);
   map<char,int> nchar;
   REP(i, N) {
      nchar[S[i]]++;
   }
   set<char> oddnchar;
   REP(i, 26) {
      char c = 'a'+i;
      if (nchar[c] % 2 == 1) {
         oddnchar.insert(c);
      }
   }

   int cost = 0;
   if (SZ(oddnchar) > 1) {
      cout << -1 << endl;
      return 0;
   }
   map<char,int> cnt;
   string pre, cen, suf;
   REP(i, N) {
      if (2*cnt[S[i]] + 1 < nchar[S[i]]) {
         pre += S[i];
         cost += SZ(suf) + SZ(cen);
      } else if (2*cnt[S[i]] + 1 == nchar[S[i]]) {
         cen += S[i];
         cost += SZ(suf);
      } else {
         suf += S[i];
      }
      cnt[S[i]]++;
   }

   map<char,stack<int>> preorder;
   FOR(i, 0, SZ(pre)) {
      preorder[pre[i]].push(i);
   }
   V<int> suforder;
   FOR(i, 0, SZ(suf)) {
      int order = preorder[suf[i]].top(); preorder[suf[i]].pop();
      suforder.PB(order);
   }

   reverse(ALL(suforder));
   cost += inversionP(suforder);

   cout << cost << endl;

   return 0;
}


Measured memory_bytes: 3200