#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define mod 1000000007LL
#define eps 1e-13
#define PI 3.141592653589793238L
#define INF 1000000011
#define INFLL 1000000000000000011LL
// #define space printf(" ")
#define endl '\n'
#define vi vector<int>
#define vll vector<long long>
#define vc vector<char>
#define vs vector<string>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pil pair<int, long long>
#define pli pair<long long, int>
#define pcc pair<char, char>
#define pdd pair<double, double>
#define mp make_pair
#define F first
#define S second
#define pb(x) push_back(x)
#define fo(i,a,n) for(i = (a); i < (n); i++)
#define sd(x) scanf("%d", &(x))
#define pd(x) printf("%d", (x))
#define pdn(x) printf("%d\n", (x))
#define slld(x) scanf("%lld", &(x))
#define plld(x) printf("%lld", (x))
#define plldn(x) printf("%lld\n", (x))
#define sllf(x) scanf("%llf", &(x))
#define pllf(x) printf("%.9llf", (x))
#define pllfn(x) printf("%.9llf\n", (x))
#define sch(x) scanf("%c", &(x))
#define pch(x) printf("%c", (x))
#define pchn(x) printf("%c\n", (x))
#define gtl(x) getline(cin, (x))
#define flsh fflush(stdout)
#define sws ios_base::sync_with_stdio(false); cin.tie(0)
#define gcd __gcd
#define clr(x) memset(x,0,sizeof(x))
#define all(a) (a).begin(), (a).end()
#define foreach(i,a) for(__typeof((a).begin()) i = (a).begin(); i != (a).end(); ++i)
#define sz(a) (int)((a).size())
#define io_file freopen("D:/Coding Problems/Contest/input_file.in", "r", stdin);freopen("D:/Coding Problems/Contest/output_file.out", "w", stdout)

ll modx(ll Base, ll exponent)
{
	ll ans = 1;
	if(Base == 1)
		return Base;
	while(exponent)
	{
		if(exponent & 1)
			ans = (ans * Base)%mod;
		Base = (Base * Base)%mod;
		exponent = exponent >> 1;
	}
	return ans;
}

ll inmodx(ll num)
{
	return (modx(num, mod-2LL));
}

bool cmp()//true for a before b
{
	bool ans = 0;
	return ans;
}

struct ST_Node
{

	ST_Node()
	{
		return;
	}
	void assign_value_(int val)
	{
		return;
	}
	void merge_nodes_(ST_Node& left, ST_Node& right)
	{
		return;
	}
};

const int N = (2e5) + 9;
const int M = (N<<2) + 9;
const int LOGN = ((int)log2(N)) + 3;
const int LOGM = ((int)log2(M)) + 3;
const int BUCK = 100;

vi ch[26];
vector < pii > p;
int new_pos[N], st[M];

void update(int node, int l, int r, int ind, int val)
{
	if(l > r || ind < l || ind > r)
		return;
	if(l == r)
	{
		st[node] = val;
		return;
	}
	int mid = (l+r)>>1;
	int left = node<<1;
	int right = left|1;
	update(left,l,mid,ind,val);
	update(right,mid+1,r,ind,val);
	st[node] = st[left] + st[right];
	return;
}

int query(int node, int l, int r, int p, int q)
{
	if(l > r || p > q || l > q || p > r)
		return 0;
	if(l >= p && r <= q)
		return st[node];
	int mid = (l+r)>>1;
	int left = node<<1;
	int right = left|1;
	return (query(left,l,mid,p,q) + query(right,mid+1,r,p,q));
}

int main()
{
	sws;
	// clock_t clk;
	// clk = clock();
	// io_file;
	// srand (time(NULL));

	//Code here
	string s;
	int n, i, cnt_odd = 0, j, cnt;
	ll ans = 0LL;
	cin >> s;
	n = s.length();
	fo(i,0,n)
		ch[s[i]-'a'].pb(i);
	fo(i,0,26)
		if(sz(ch[i])&1)
			cnt_odd++;
	if(cnt_odd <= 1)
	{
		fo(i,0,26)
		{
			fo(j,0,(sz(ch[i])/2))
				p.pb(mp(ch[i][j],ch[i][sz(ch[i])-1-j]));
			if(sz(ch[i])&1)
				p.pb(mp(ch[i][(sz(ch[i])/2)],ch[i][(sz(ch[i])/2)]));
		}
		sort(all(p));
		cnt = 0;
		fo(i,0,sz(p))
		{
			if(p[i].F != p[i].S)
			{
				new_pos[p[i].F] = cnt;
				new_pos[p[i].S] = n-1-cnt;
				cnt++;
			}
			else
				new_pos[p[i].F] = (n/2);
		}
		fo(i,0,n)
		{
			ans += (ll)query(1,0,n,new_pos[i],n-1);
			update(1,0,n,new_pos[i],1);
		}
	}
	else
		ans = -1;
	cout << ans << '\n';
	// Code ends here

	// clk = clock() - clk;
	// cerr << fixed << setprecision(6) << "Time: " << ((double)clk)/CLOCKS_PER_SEC << "\n";
	return 0;
}

Measured memory_bytes: 6028