#include <bits/stdc++.h>
using namespace std;

#ifdef SG
	#include <debug.h>
#else
	template<typename T> struct outputer;
	struct outputable {};
	#define PRINT(...)
	#define OUTPUT(...)
	#define show(...)
	#define debug(...)
	#define deepen(...)
	#define timer(...)
	#define fbegin(...)
	#define fend
	#define pbegin(...)
	#define pend
#endif

#define ARG4(_1,_2,_3,_4,...) _4

#define forn3(i,l,r) for (int i = int(l); i < int(r); ++i)
#define forn2(i,n) forn3 (i, 0, n)
#define forn(...) ARG4(__VA_ARGS__, forn3, forn2) (__VA_ARGS__)

#define ford3(i,l,r) for (int i = int(r) - 1; i >= int(l); --i)
#define ford2(i,n) ford3 (i, 0, n)
#define ford(...) ARG4(__VA_ARGS__, ford3, ford2) (__VA_ARGS__)

#define ve vector
#define pa pair
#define tu tuple
#define mp make_pair
#define mt make_tuple
#define pb emplace_back
#define fs first
#define sc second
#define all(a) (a).begin(), (a).end()
#define sz(a) ((int)(a).size())

typedef long double ld;
typedef int64_t ll;
typedef uint64_t ull;
typedef uint32_t ui;
typedef uint16_t us;
typedef uint8_t uc;
typedef pa<int, int> pii;
typedef pa<int, ll> pil;
typedef pa<ll, int> pli;
typedef pa<ll, ll> pll;
typedef ve<int> vi;

template<typename T> inline auto sqr (T x) -> decltype(x * x) {return x * x;}
template<typename T1, typename T2> inline bool umx (T1& a, T2 b) {if (a < b) {a = b; return 1;} return 0;}
template<typename T1, typename T2> inline bool umn (T1& a, T2 b) {if (b < a) {a = b; return 1;} return 0;}

const int N = 200000;
const int C = 26;

struct Input {
	string s;
	
	bool read () {
		return !!getline(cin, s);
	}

	void init (const Input &input) {
		*this = input;
	}
};

struct Data: Input {
	ll ans;
	
	void write () {
		cout << ans << endl;
	}
};


namespace Main {
	
	struct Solution: Data {
		int t[N + 2];
		
		void add (int k, int val) {
			for (int i = k; i < N; i |= i + 1) {
				t[i + 1] += val;
			}
		}
		
		int get (int k) {
			int res = 0;
			for (int i = k; i; i &= i - 1) {
				res += t[i];
			}
			return res;
		}
		
		int n;
		vi v[C];
		
		int p[N];
		
		void solve () {
			memset(t, 0, sizeof t);
			n = sz(s);
			forn (i, n) {
				v[s[i] - 'a'].pb(i);
			}
			int cnt = 0;
			forn (i, C) {
				if (sz(v[i]) % 2 == 1) {
					cnt++;
				}
				forn (j, sz(v[i])) {
					p[v[i][j]] = v[i][sz(v[i]) - 1 - j];
				}
			}
			if (cnt > 1) {
				ans = -1;
				return;
			}
			
			ans = 0;
			forn (i, n) {
				if (p[i] > i) {
					ans += get(p[i]);
					add(p[i], 1);
				} else if (p[i] < i) {
					add(p[i], 1);
				} else {
					forn (j, n) {
						if (p[j] > j) {
							if (p[j] < i || j > i) {
								ans += 1;
							}
						}
					}
				}
			}
		}
		
		void clear () {
			*this = Solution();
		}
	};
}


Main::Solution sol;

int main () {
	cout.setf(ios::showpoint | ios::fixed);
	cout.precision(20);

	#ifdef SG
		freopen((problemname + ".in").c_str(), "r", stdin);
//		freopen((problemname + ".out").c_str(), "w", stdout);
		while (sol.read()) {
			sol.solve();
			sol.write();
			sol.clear();
		}
	#else
		sol.read();
		sol.solve();
		sol.write();
	#endif
	
	/*
	int t;
	cin >> t;
	forn (i, t) {
		sol.read();
		sol.solve();
		sol.write();
		sol.clear();
	}
	*/
	
	return 0;
}


Measured memory_bytes: 3068