#include <bits/stdc++.h>
using namespace std;
// define
#define int long long
#define UNIQUE(v) v.erase(unique(all(v)), v.end());
#define ZIP(v) sort(all(v)),UNIQUE(v)
#define ADD(a, b) a = (a + b) % mod
#define SUB(a, b) a = (a+mod-b)%mod
#define MUL(a, b) a = (((a)%mod) * ((b)%mod)) % mod
#define rollcall cout << "I'm Sucu." << endl;
#define repi(i,m,n) for(int i = m;i < n;i++)
#define drep(i,n,m) for(int i = n;i >= m;i--)
#define rep(i,n) repi(i,0,n)
#define rrep(i,n) repi(i,1,n+1)
#define chmin(x,y) x = min(x,y)
#define chmax(x,y) x = max(x,y)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(), v.rend()
#define dmp(x,y) make_pair(x,y)
#define dmt(x, y, z) make_tuple(x, y, z)
#define pb(x) push_back(x)
#define pf(x) push_front(x)
#define fi first
#define se second
// debug
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p){
  os << "(" << p.first << "," << p.second << ")";return os;
}
template <typename T, typename U, typename V>
ostream &operator<<(ostream &os, const tuple<T, U, V> &t){
  os << "(" << get<0>(t) << "," << get<1>(t) << "," << get<2>(t) << ")";
  return os;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v){
  for (auto it = v.begin();it != v.end();++it){
    if(it != v.begin())os << " ";os << *it;
  }return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &mp){
  for(auto x: mp)os << "(" << x.first << "," << x.second << ")" << endl;
  return os;
}
template<typename T, int SIZE>
int array_length(const T (&)[SIZE]){return SIZE;}
template<typename T, int N>
void PRINTF(const T (&a)[N], int s = N, int t = -1, bool f = true){
	if(t == -1){rep(i,s){if(i)cout << " ";cout << a[i];}}
	else repi(i,s,t){if(i!=s)cout << " ";cout << a[i];}
	if(f)cout << "\n";
}
template<typename T, int N1, int N2>
void PRINTF(const T (&a)[N1][N2], int h = N1, int w = N2){
	rep(i,h){rep(j,w){cout << a[i][j] << " \n"[j==w-1];}}
}
string substr(const string &str, int S1, int S2 = -1){
  if(S2 == -1)return str.substr(S1);
  return str.substr(S1, S2-S1);
}
// typedef
typedef complex<double> Point;
typedef pair<int, int> P;
typedef pair<int, P> PP;
typedef pair<P, int> Pi;
typedef tuple<int, int, int> TT;
typedef pair<int, TT> PT;
typedef vector<int> vi;
typedef deque<int> dq;
const int inf = 1e9+7;
const int INF = 1e18+7;
// int sum = accumulate(a, a+n, 0LL);
// int mx = max_element(a, a+n);
// int mn = min_element(a, a+n);
// int cnt = count(a, a+n, k);


// 0に対応できるよう内部でindexを1ずらしてる
class BIT{
public:
	int n = 1;
	vector<int> bit;
	void init(int N){	//[0, N)のBIT作成
		while(n < N+1)n *= 2;
		bit.resize(n+1);
		fill(all(bit), 0);
	}
	void add(int i, int x){
		i++;while(i <= n){bit[i] += x;i += i&-i;}
	}
	int get(int i){
		int s = 0;i++;
		while(i > 0){s += bit[i];i -= i&-i;}
		return s;
	}
	int lower_bound(int k){
		int lb = -1, ub = n;
		while(ub-lb > 1){
			if(get((lb+ub)/2) >= k)ub = (lb+ub)/2;
			else lb = (lb+ub)/2;
		}
		return ub;
	}
};

int solve(int n, vector<int> v){
  BIT bit;bit.init(n);
  int ans = 0;
  rep(i,n){
    int res = bit.get(v[i]);
    ans += i-res;
    bit.add(v[i], 1);
  }
  return ans;
}

int a[50], b[50];
signed main(){
  string str, T;cin >> str;
  int n = str.size(), cnt = 0;
  rep(i,n)a[str[i]-'a']++;
  rep(i,26)cnt += (a[i]%2 == 1);
  if(cnt >= 2){
    cout << -1 << endl;
    return 0;
  }
  
  int t1 = 0, t2 = (n%2 == 1);
  vector<int> vec;
  string A = "", B = "", C = "";
  rep(i,n){
    int c = str[i]-'a';b[c]++;
    if(a[c]%2 == 1 and b[c] == a[c]/2+1){
      vec.pb(n/2);B.pb(c+'a');continue;
    }
    if(b[c] <= a[c]/2){
      A.pb(c+'a');vec.pb(t1);t1++;
    }else{
      C.pb(c+'a');vec.pb(n/2+t2);t2++;
    }
  }
  T = A + B + C;
  int ans = solve(n, vec);
  
  vector<int> d[50], vec2;
  rep(i,n/2)d[T[i]-'a'].pb(n-i-1-((n+1)/2));
  int l = (n+1)/2, r = n;
  repi(i,l,r){
    int tmp = d[T[i]-'a'].back();d[T[i]-'a'].pop_back();
    vec2.pb(tmp);
  }
  
  // cout << T << endl;
  // cout << vec2 << endl;
  ans += solve(r-l, vec2);
  cout << ans << endl;
  return 0;
}






Measured memory_bytes: 7252