#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <functional>
#define _USE_MATH_DEFINES
#include <cmath>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cfloat>
#include <cmath>
#include <ctime>
#include <cstdio>
#include <cassert>
using namespace std;

#define EPS 1e-12
#define ull unsigned long long
#define ll long long
#define VI vector<ll>
#define PII pair<ll, ll> 
#define VVI vector<vector<ll> >
#define REP(i,n) for(int i=0,_n=(n);(i)<(int)_n;++i)
#define RANGE(i,a,b) for(int i=(int)a,_b=(int)(b);(i)<_b;++i)
#define ALL(c) (c).begin(), (c).end()
#define ALLR(c) (c).rbegin(), (c).rend()
#define PB push_back
#define MP(a, b) make_pair(a, b)
#define POPCOUNT __builtin_popcount
#define POPCOUNTLL __builtin_popcountll
#define CLEAR(table, v) memset(table, v, sizeof(table));
#define PRINT1(table, D0) REP(d0, D0) cout<<table[d0]<<" "; cout<<"\n";
#define PRINT2(table, D0, D1) REP(d0, D0) { REP(d1, D1) cout<<table[d0][d1]<<" "; cout<<"\n"; }
#define PRINT3(table, D0, D1, D2) REP(d0, D0) { REP(d1, D1) { REP(d2, D2) cout<<table[d0][d1][d2]<<" "; cout<<"\n"; } cout<<"\n"; }
#define UNIFORM_DOUBLE(a, b) (((b-a)*(double)rand()/RAND_MAX)+a) // [a, b) 
#define UNIFORM_LL(a, b) (ll)UNIFORM_DOUBLE(a, b) // [a, b) 
#define IN(v, lo, hi) ((lo)<=(v) && (v)<(hi))
#define DD(v) cout<<#v<<": "<<v<<endl
template <typename T0, typename T1> std::ostream& operator<<(std::ostream& os, const map<T0, T1>& v) { for( typename map<T0, T1>::const_iterator p = v.begin(); p!=v.end(); p++ ){os << p->first << ": " << p->second << " ";} return os; }
template <typename T0, typename T1> std::ostream& operator<<(std::ostream& os, const pair<T0, T1>& v) { os << v.first << ": " << v.second << " "; return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const vector<T>& v) { for( int i = 0; i < (int)v.size(); i++ ) { os << v[i] << " "; } return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const vector<vector<T> >& v) { for( int i = 0; i < (int)v.size(); i++ ) { os << v[i] << endl; } return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const set<T>& v) { vector<T> tmp(v.begin(), v.end()); os << tmp; return os; }
template <typename T> std::ostream& operator<<(std::ostream& os, const deque<T>& v) { vector<T> tmp(v.begin(), v.end()); os << tmp; return os; }

#define MOD 1000000007LL
#define INF (1LL<<60)




using namespace std;
#define FOR(i,n) for(int i = 0; i < (n); i++)
#define sz(c) ((int)c.size())
#define ten(n) ((int)1e##n)
using Pii = pair<int, int>;
using Pll = pair<ll, ll>;
 
 
template<class T> void chmin(T& a, const T& b) { if (a > b) a = b; }
template<class T> void chmax(T& a, const T& b) { if (a < b) a = b; }
 
template<class T> T gcd(T a, T b) { return b ? gcd(b, a % b) : a; }
template<class T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
ll mod_pow(ll a, ll n, ll mod) {
	ll ret = 1;
	ll p = a % mod;
	while (n) {
		if (n & 1) ret = ret * p % mod;
		p = p * p % mod;
		n >>= 1;
	}
	return ret;
}
template<class T> T extgcd(T a, T b, T& x, T& y) { for (T u = y = 1, v = x = 0; a;) { T q = b / a; swap(x -= q * u, u); swap(y -= q * v, v); swap(b -= q * a, a); } return b; }
template<class T> T mod_inv(T a, T m) { T x, y; extgcd(a, m, x, y); return (m + x % m) % m; }
 
ll mergecount(vector<int> &a) {
	ll count = 0;
	int n = a.size();
	if (n > 1) {
		vector<int> b(a.begin(), a.begin() + n / 2);
		vector<int> c(a.begin() + n / 2, a.end());
		count += mergecount(b);
		count += mergecount(c);
		for (int i = 0, j = 0, k = 0; i < n; ++i)
			if (k == c.size())       a[i] = b[j++];
			else if (j == b.size())  a[i] = c[k++];
			else if (b[j] <= c[k])   a[i] = b[j++];
			else { a[i] = c[k++]; count += n / 2 - j; }
	}
	return count;
}
 
ll ref(string s) {
	map<char, vector<int>> mp;
	vector<int> idx;
	FOR(i, sz(s)) {
		idx.push_back(sz(mp[s[i]]));
		mp[s[i]].push_back(i);
	}
 
	bool ok = true;
	int shouldBeCenter = -1;
	int used = 0;
	vector<int> vs(sz(s));
	{
		FOR(i, sz(s)) {
			int curidx = idx[i];
			auto& v = mp[s[i]];
			if (sz(v) % 2 == 1 && curidx == sz(v) / 2) {
				if (shouldBeCenter == -1) {
					shouldBeCenter = 0;
					vs[v[sz(v) / 2]] = sz(s) / 2;
				} else {
					ok = false;
					break;
				}
			} else if (curidx < sz(v) / 2) {
				vs[i] = used;
				vs[v[sz(v) - 1 - curidx]] = sz(s) - 1 - used;
				used++;
			}
		}
	}
 
	if (!ok) {
		return -1;
	}
 
	// writerArr(vs);
 
	ll ans = mergecount(vs);
	return ans;
}


template<typename T>
struct BIT {
	vector<T> w;
	BIT(int N) { w = vector<T>(N); }
	// sum of w[i], i in [l, r]
	T sum(int l, int r) {
		if(l==0) {
			T s=0;
			for(;r>=0;r=(r&(r+1))-1) s+=w[r];
			return s;
		}
		return sum(0, r) - sum(0, l-1);
	}
	// i in [0, N)
	void add(int i, T v) {
		for(;i<(int)w.size();i|=i+1) w[i] += v;
	}
};
template<typename T>
ll inversion_number(const vector<T>& d) {
	ll N = d.size();
	BIT<T> bit(N);
	ll cnt = 0;
	for(int i=N-1;i>=0;i--) {
		cnt += bit.sum(0, d[i]);
		bit.add(d[i], 1);
	}
	return cnt;
}

ll solve(string s) {
	ll ans = 0;
	map<char, int> hi;
	ll N = s.size();
	REP(i, N) hi[s[i]]++;
	VI co(2);
	for(auto kv : hi) co[kv.second % 2]++;
	if(co[1]>=2) ans = -1;
	else {
		VI p(N);
		vector<bool> isL(N);
		map<int, VI> cvs;
		REP(ci, 26) {
			VI vs;
			REP(i, N) if(s[i]=='a'+ci) vs.PB(i);
			REP(i, vs.size()/2) isL[vs[i]] = 1;
			if(vs.size()%2==1) p[N/2] = vs[vs.size()/2];
			cvs[ci] = vs;
		}
//			DD(isL);
		int ai=0;
		REP(i, N) if(isL[i]) p[ai++] = i;
		VI co(26);
		REP(i, N/2) {
			int ci = s[p[i]]-'a';
			auto& vs = cvs[ci];
			p[N-1-i] = vs[vs.size()-1-co[ci]];
			co[ci]++;
		}
//			DD(p);
		string t(N, ' ');
		REP(i, N) t[i] = s[p[i]];
//			DD(t);
		REP(i, N) assert(0<=p[i]&&p[i]<N);
		ans = inversion_number(p);
	}
	return ans;
}
void test() {
	REP(loop, 1000) {
		ll N = UNIFORM_LL(3, 20);
		string s(N, ' ');
		REP(i, N) s[i] = UNIFORM_LL(0, 5)+'a';
		N += N;
		s += s;
		ll refAns = ref(s);
		ll ans = solve(s);
		DD(s);
		if(refAns!=ans) {
			DD(s);
			DD(refAns);
			DD(ans);
			assert(0);
		}
	}
}
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
//	test();
	string s;
	while(cin>>s) {
		ll ans = solve(s);
		cout<<ans<<endl;
	}
	
	return 0;
}


Measured memory_bytes: 6464