#include <bits/stdc++.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

#define _all(arg) begin(arg),end(arg)
#define uniq(arg) sort(_all(arg)),(arg).erase(unique(_all(arg)),end(arg))
#define getidx(ary,key) lower_bound(_all(ary),key)-begin(ary)
#define clr(a,b) memset((a),(b),sizeof(a))
#define bit(n) (1LL<<(n))
#define popcount(n) (__builtin_popcountll(n))

using namespace std;

template<class T>bool chmax(T &a, const T &b) { return (a < b) ? (a = b, 1) : 0;}
template<class T>bool chmin(T &a, const T &b) { return (b < a) ? (a = b, 1) : 0;}

using ll = long long;
using R = long double;
const R EPS = 1e-9L; // [-1000,1000]->EPS=1e-8 [-10000,10000]->EPS=1e-7
inline int sgn(const R& r) {return (r > EPS) - (r < -EPS);}
inline R sq(R x) {return sqrt(max(x, 0.0L));}

const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};

#define error(args...) { vector<string> _debug = split(#args, ',');err(begin(_debug), args);}

vector<string> split(const string& s, char c){
	vector<string> v;stringstream ss(s);string x;
	while (getline(ss, x, c)) v.emplace_back(x);
	return move(v);
}

void err(vector<string>::iterator it) {cerr << endl;}
template<typename T, typename... Args> void err(vector<string>::iterator it, T a,Args... args){
	cerr << it -> substr((*it)[0] == ' ', it -> length()) << " = " << a << " ",err(++it, args...);
}

template <int depth> struct Binary_indexed_tree {
	using T = ll;

	const static int h = depth;
	const static int n = 1 << h;
	T data[n];

	void init() {
		fill_n(data, n, 0);
	}

	void update(int i, T x) {
		for (i++; i < n; i += i & -i) {
			data[i] += x;
		}
	}

	T query(int i) {
		T ret = 0;
		for (i++; i > 0; i -= i & -i) ret += data[i];
		return ret;
	}
};

Binary_indexed_tree<18> bit;

ll solve(string a, string b) {
	const int n = a.size();
	vector<int> num(26, 0);

	rep(i, n) num[a[i] - 'a']++;

	vector<int> ary(n, 0);	

	rep(c, 26) {
		int from = 0, to = 0;
		rep(loop, num[c]) {
			while(a[from] != char(c + 'a')) from++;
			while(b[to] != char(c + 'a')) to++;
			ary[to] = from;
			from++, to++;
		}
	}

	ll ret = 0LL;
	bit.init();
	rep(i, n) {
		ret += i - bit.query(ary[i]);
		bit.update(ary[i], 1);
	}

	return ret;
}


int main(void) {
	string s;
	cin >> s;
	const int n = s.size();

	vector<int> num(26, 0);
	rep(i, n) num[s[i] - 'a']++;
	
	int odd = 0;
	rep(i, 26) odd += num[i] & 1;

	if (odd > n % 2) {
		puts("-1");
		return 0;
	}

	vector<int> cnt(26, 0);
	string pre = "", cetner = "", post = "";
	
	rep(i, n) {
		const int c = s[i] - 'a';
		if(cnt[c] < num[c] / 2) {
			pre += s[i]; 
		} else if(num[c] % 2 == 1 and cnt[c] == num[c] / 2) {
			cetner += s[i];
		} else {
			post += s[i];
		}
		cnt[c]++;
	}

	const string t = pre + cetner + post;
	string post_rev = post;
	reverse(begin(post_rev), end(post_rev));

	const ll ans = solve(pre, post_rev) + solve(s, t);
	cout << ans << endl;

	return 0;
}

Measured memory_bytes: 4476