#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/detail/standard_policies.hpp>
using namespace __gnu_pbds;

#if !ONLINE_JUDGE
#define debug
#endif

using namespace std;
 
/*******  All Required define Pre-Processors and typedef Constants *******/
#define mem(a, b) memset(a, (b), sizeof(a))
#define repd(i,k) for(int i=k;i>=0;i--)
#define rep(i,k) for(int i=0;i<k;i++)
#define repn(i,k1,k2) for(ll i=k1;i<k2;i++)
#define sz(x) (ll)(x).size()
#define ff first
#define ss second

#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define INF (int)1e9
#define EPS 1e-9
#define PI 3.1415926535897932384626433832795
#define MOD 1000000007
#define ee6 (ll)1000001
#define ee5 (ll)100001

#define trav(a, v) for(auto& a : v)

#define tt ll t;cin>>t; while(t--)
typedef long long int ll;
 
typedef pair<ll, ll> pr;
typedef vector<ll> vi;
typedef vector<string> vs;
typedef vector<pr> vpr;
typedef vector<vpr>vvpr;
typedef vector<vi> vvi;

//*X.find_by_order(2) element at index=2
//X.order_of_key(1) how many elements strictly less than 1

template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,
    tree_order_statistics_node_update>;

#ifdef debug
#define dbg(...) { cerr<<"[ "; dump(#__VA_ARGS__, __VA_ARGS__);}
#undef endl
template <typename Arg1,typename Arg2>
ostream& operator << (ostream& out, const pair<Arg1,Arg2> &x) {
    return out<<"("<<x.ff<<","<<x.ss<<")";
}
 
template <typename Arg1>
ostream& operator << (ostream& out, const vector<Arg1> &a) {
    out<<"[";for(const auto &x:a)out<<x<<",";return out<<"]";
}
 
template <typename Arg1>
ostream& operator << (ostream& out, const set<Arg1> &a) {
    out<<"[";for(const auto &x:a)out<<x<<",";return out<<"]";
}
 
template <typename Arg1,typename Arg2>
ostream& operator << (ostream& out, const map<Arg1,Arg2> &a) {
    out<<"[";for(const auto &x:a)out<<x<<",";return out<<"]";
}
 
template <typename Arg1,typename Arg2>
ostream& operator << (ostream& out, const unordered_map<Arg1,Arg2> &a) {
    out<<"[";for(const auto &x:a)out<<x<<",";return out<<"]";
} 
 
template <typename Arg1>
void dump(const string name, Arg1&& arg1){
    cerr << name << " : " << arg1 << " ] " << endl;
}
 
template <typename Arg1, typename... Args>
void dump(const string names, Arg1&& arg1, Args&&... args){
    const string name = names.substr(0,names.find(','));
    cerr<<name<<" : "<<arg1<<" | ";
    dump(names.substr(1+(int)name.size()), args...);
}
#else
    #define dbg(args...)
#endif
 
ll powmod(ll x, ll y) 
{ 
    ll res = 1;  
    x = x % MOD;
    while (y > 0) 
    { 
        if (y & 1) 
            res = (res*x) % MOD; 
        y = y>>1; // y = y/2 
        x = (x*x) % MOD;   
    } 
    return res; 
} 
vector<ll>mt[27],anst[27];
set<pair<ll,ll> >st;
int main()
{
    #if !ONLINE_JUDGE
//    freopen("in.txt","r",stdin);
    #endif
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    string s;cin>>s;
    ll n=s.size();
    for(ll i=0;i<n;i++){
        mt[s[i]-97].pb(i);
    }      
    
    ll ch=-1;
    for(ll i=0;i<26;i++){
        ll cnt=mt[i].size();
        ll sz=cnt;
        ll l=0;
        while(cnt>1){            
                ll x=mt[i][l],y=mt[i][sz-1-l];
                st.insert(mp(x+n-y,i));
                l++;         
                cnt-=2;   
        }
        if(cnt==1){
            if(~ch){cout<<"-1";exit(0);}
            ch=i;
        }
    }
    string ans;
    while(!st.empty()){
        char ch=97+st.begin()->ss;
        ans.pb(ch);
        st.erase(st.begin());
    }
    string rev(ans.rbegin(),ans.rend());
    if(~ch)ans.pb(97+ch);    
    ans.append(rev);

    for(int i=0;i<26;i++)
        reverse(all(mt[i]));

    ll inv=0;
    ordered_set<int>od;
    rep(i,n)od.insert(i);
    for(auto e:ans){
        int x=mt[e-97].back();
        mt[e-97].pop_back();
        ll y=od.order_of_key(x);       
        inv+=y;
        od.erase(x);
    }
    cout<<inv;

}

Measured memory_bytes: 11916